Abstract:
We consider a Hankel determinant formula for generic solutions of the Painlev\'e IV equation. We show that the generating functions for the entries of the Hankel determinants are related to the asymptotic solution at infinity of the isomonodromic problem. Summability of these generating functions are also discussed.

Abstract:
The Hankel determinants of certain automatic sequences $f$ are evaluated, based on a calculation modulo a prime number. In most cases, the Hankel determinants of automatic sequences do not have any closed-form expressions; the traditional methods, such as $LU$-decompo\-si\-tion and Jacobi continued fraction, cannot be applied directly. Our method is based on a simple idea: the Hankel determinants of each sequence $g$ equal to $f$ modulo $p$ are equal to the Hankel determinants of $f$ modulo $p$. The clue then consists of finding a nice sequence $g$, whose Hankel determinants have closed-form expressions. Several examples are presented, including a result saying that the Hankel determinants of the Thue-Morse sequence are nonzero, first proved by Allouche, Peyri\`ere, Wen and Wen using determinant manipulation. The present approach shortens the proof of the latter result significantly. We also prove that the corresponding Hankel determinants do not vanish when the powers $2^n$ in the infinite product defining the $\pm 1$ Thue--Morse sequence are replaced by $3^n$.

Abstract:
In the paper, we give the recurrent equations of the Hankel determinants of the Cantor sequence, and show that the Hankel determinants as a double sequence is 3-automatic. With the help of the Hankel determinants, we prove that the irrationality exponent of the Cantor number, i.e. the transcendental number with Cantor sequence as its b-ary expansion, equals 2.

Abstract:
The estimates for the second Hankel determinant a_2a_4-a_3^2 of analytic function f(z)=z+a_2 z^2+a_3 z^3+...b for which either zf'(z)/f(z) or 1+zf"(z)/f'(z) is subordinate to certain analytic function are investigated. The estimates for the Hankel determinant for two other classes are also obtained. In particular, the estimates for the Hankel determinant of strongly starlike, parabolic starlike, lemniscate starlike functions are obtained.

Abstract:
Let f be analytic in D={z:|z|<1} with f(0)=0 and f'(0)=1. We give sharp bounds for the second Hankel determinant of f, when f is starlike of order alpha in D.

Abstract:
We continue with the study of the Hankel determinant, $$ D_{n}(t,\alpha,\beta):=\det\left(\int_{0}^{1}x^{j+k}w(x;t,\alpha,\beta)dx\right)_{j,k=0}^{n-1}, $$ generated by a Pollaczek-Jacobi type weight, $$ w(x;t,\alpha,\beta):=x^{\alpha}(1-x)^{\beta}{\rm e}^{-t/x}, \quad x\in [0,1], \quad \alpha>0, \quad \beta>0, \quad t\geq 0. $$ This reduces to the "pure" Jacobi weight at $t=0.$ We may take $\alpha\in \mathbb{R}$, in the situation while $t$ is strictly greater than $0.$ It was shown in Chen and Dai (2010), that the logarithmic derivative of this Hankel determinant satisfies a Jimbo-Miwa-Okamoto $\sigma$-form of Painlev\'e \uppercase\expandafter{\romannumeral5} (${\rm P_{\uppercase\expandafter{\romannumeral5}}}$). In fact the logarithmic of the Hankel determinant has an integral representation in terms of a particular ${\rm P_{\uppercase\expandafter{\romannumeral5}}}.$ \\ In this paper, we show that, under a double scaling, where $n$ the dimension of the Hankel matrix tends to $\infty$, and $t$ tends to $0^{+},$ such that $s:=2n^2t$ is finite, the double scaled Hankel determinant (effectively an operator determinant) has an integral representation in terms of a particular ${\rm P_{\uppercase\expandafter{\romannumeral3}'}}.$ Expansions of the scaled Hankel determinant for small and large $s$ are found. A further double scaling with $\alpha=-2n+\lambda,$ where $n\rightarrow \infty$ and $t,$ tends to $0^{+},$ such that $s:=nt$ is finite. In this situation the scaled Hankel determinant has an integral representation in terms of a particular ${\rm P_{\uppercase\expandafter{\romannumeral5}}},$ %which can be degenerate to a particular ${\rm P_{\uppercase\expandafter{\romannumeral3}}}$ and its small and large $s$ asymptotic expansions are also found.

Abstract:
The objective of the present paper is to obtain the sharp upper bound of for p-valent α-convex functions of the form in the unit disc . 1. Introduction Let be the class of analytic functions of the form in the unit disc with . Let be the subclass of , consisting of univalent functions. is the class consisting of functions of the form (1) and satisfying the condition The functions of the class are called p-valent starlike functions. In particular, , the class of starlike functions. is the class of functions of the form (1), satisfying the condition The functions of the class are known as p-valent convex functions. Particularly, , the class of convex functions. Obviously if and only if . Let be the class of functions of the form (1), satisfying the condition Functions in the class are known as -valent alpha-convex functions. For , the class reduces to the class of alpha-convex functions introduced by Mocanu [1]. Also and . In 1976, Noonan and Thomas [2] stated the th Hankel determinant for and as This determinant has also been considered by several authors. For example, Noor [3] determined the rate of growth of as for functions given by (1) with bounded boundary. Ehrenborg [4] studied the Hankel determinant of exponential polynomials. Also Hankel determinant was studied by various authors including Hayman [5] and Pommerenke [6]. In [7], Janteng et al. studied the Hankel determinant for the classes of starlike and convex functions. Again Janteng et al. discussed the Hankel determinant problem for the classes of starlike functions with respect to symmetric points and convex functions with respect to symmetric points in [8] and for the functions whose derivative has a positive real part in [9]. Also Hankel determinant for various subclasses of -valent functions was investigated by various authors including Krishna and Ramreddy [10] and Hayami and Owa [11]. Easily, one can observe that the Fekete and Szeg？ functional is . Fekete and Szeg？ [12] then further generalised the estimate , where is real and . For our discussion in this paper, we consider the Hankel determinant in the case of and : In this paper, we seek sharp upper bound of the functional for functions belonging to the class . The results due to Janteng et al. [7] follow as special cases. 2. Preliminary Results Let be the family of all functions analytic in for which and for . Lemma 1 (see [6]). If , then Lemma 2 (see [13, 14]). If , then for some and satisfying and . 3. Main Result Theorem 3. If , then where Proof . Since , so from (4) On expanding and equating the coefficients of , and in (11), we

Abstract:
In the present paper, we will discuss the Hankel determinants $H(f) =a_2a_4-a_3^2$ of order 2 for normalized concave functions $f(z)=z+a_2z^2+a_3z^3+\dots$ with a pole at $p\in(0,1).$ Here, a meromorphic function is called concave if it maps the unit disk conformally onto a domain whose complement is convex. To this end, we will characterize the coefficient body of order 2 for the class of analytic functions $\varphi(z)$ on $|z|<1$ with $|\varphi|<1$ and $\varphi(p)=p.$ We believe that this is helpful for other extremal problems concerning $a_2, a_3, a_4$ for normalized concave functions with a pole at $p.$

Abstract:
We give an explicit evaluation, in terms of products of Jacobsthal numbers, of the Hankel determinants of order a power of two for the period-doubling sequence. We also explicitly give the eigenvalues and eigenvectors of the corresponding Hankel matrices. Similar considerations give the Hankel determinants for other orders.

Abstract:
In this paper, we construct the Hankel determinant representationof the rational solutions for the fifth Painlev′e equation through theUmemura polynomials. Our construction gives an explicit form of theUmemura polynomials σn for n ≥ 0 in terms of the Hankel Determinantformula. Besides, We compute the generating function of the entries interms of logarithmic derivative of the Heun Confluent Function.