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Hankel determinants of the Thue-Morse sequence

Jean-Paul Allouche, Jacques Peyrière, Zhi-Xiong Wen, Zhi-Ying Wen (1998)

Annales de l'institut Fourier

Let ϵ = ( ϵ n ) n 0 be the Thue-Morse sequence, i.e., the sequence defined by the recurrence equations: ϵ 0 = 1 , ϵ 2 n = ϵ n , ϵ 2 n + 1 = 1 - ϵ n . We consider { | n p | } n 1 , p 0 , the double sequence of Hankel determinants (modulo 2) associated with the Thue-Morse sequence. Together with three other sequences, it obeys a set of sixteen recurrence equations. It is shown to be automatic. Applications are given, namely to combinatorial properties of the Thue-Morse sequence and to the existence of certain Padé approximants of the power series n 0 ( - 1 ) ϵ n x n .

Heights of squares of Littlewood polynomials and infinite series

Artūras Dubickas (2012)

Annales Polonici Mathematici

Let P be a unimodular polynomial of degree d-1. Then the height H(P²) of its square is at least √(d/2) and the product L(P²)H(P²), where L denotes the length of a polynomial, is at least d². We show that for any ε > 0 and any d ≥ d(ε) there exists a polynomial P with ±1 coefficients of degree d-1 such that H(P²) < (2+ε)√(dlogd) and L(P²)H(P²)< (16/3+ε)d²log d. A similar result is obtained for the series with ±1 coefficients. Let A m be the mth coefficient of the square f(x)² of a unimodular...

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