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A218260 E.g.f.: Sum_{n>=0} Product_{k=1..n} tanh((2*k-1)*x). 2
1, 1, 6, 88, 2280, 92416, 5393376, 428428288, 44450655360, 5836916064256, 946245183223296, 185613384522661888, 43330332249288714240, 11871318610487327850496, 3772031142226151742038016, 1375871976238663365598117888 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

Vaclav Kotesovec, Table of n, a(n) for n = 0..150

FORMULA

E.g.f.: Sum_{n>=0} Product_{k=1..n} (1 - exp(-2*(2*k-1)*x)) / (1 + exp(-2*(2*k-1)*x)).

a(n) ~ 2^(4*n+7/2) * n^(2*n+1) / (exp(2*n) * Pi^(2*n+1)). - Vaclav Kotesovec, Nov 02 2014

EXAMPLE

E.g.f.: A(x) = 1 + x + 6*x^2/2! + 88*x^3/3! + 2280*x^4/4! + 92416*x^5/5! +...

where

A(x) = 1 + tanh(x) + tanh(x)*tanh(3*x) + tanh(x)*tanh(3*x)*tanh(5*x) + tanh(x)*tanh(3*x)*tanh(5*x)*tanh(7*x) +...

PROG

(PARI) {a(n)=local(X=x+x*O(x^n), Egf); Egf=sum(m=0, n, prod(k=1, m, tanh((2*k-1)*X))); n!*polcoeff(Egf, n)}

for(n=0, 30, print1(a(n), ", "))

CROSSREFS

Cf. A002105, A221080.

Sequence in context: A178296 A122770 A265267 * A177567 A177563 A177569

Adjacent sequences:  A218257 A218258 A218259 * A218261 A218262 A218263

KEYWORD

nonn

AUTHOR

Paul D. Hanna, Oct 24 2012

STATUS

approved

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Last modified July 4 14:15 EDT 2020. Contains 335448 sequences. (Running on oeis4.)