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A110152 G.f.: A(x) = Product_{n>=1} 1/(1 - 2^n*x^n)^(2/2^n). 5
1, 2, 6, 14, 36, 78, 192, 406, 942, 2018, 4512, 9450, 21178, 43950, 95532, 200398, 431356, 892518, 1917572, 3950614, 8410230, 17398466, 36648980, 75326754, 159199004, 326471706, 683028924, 1404145162, 2930071798, 5993625942 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Vaclav Kotesovec, Table of n, a(n) for n = 0..1000

FORMULA

G.f.: exp( Sum_{n>=1} 2*A090879(n)*x^n/n ), where A090879(n) = Sum_{d|n} d*2^(n-d). - Paul D. Hanna, Jan 05 2014

EXAMPLE

G.f.: A(x) = 1 + 2*x + 6*x^2 + 14*x^3 + 36*x^4 + 78*x^5 +...

where

A(x) = 1/((1-2*x) * (1-4*x^2)^(1/2) * (1-8*x^3)^(1/4) * (1-16*x^4)^(1/8) *...).

MATHEMATICA

nmax = 30; CoefficientList[Series[Product[1/(1 - 2^k*x^k)^(2/2^k), {k, 1, nmax}], {x, 0, nmax}], x] (* Vaclav Kotesovec, Oct 18 2020 *)

PROG

(PARI) a(n)=polcoeff(prod(k=1, n, 1/(1-2^k*x^k+x*O(x^n))^(2/2^k)), n)

(PARI) A090879(n) = sumdiv(n, d, d*2^(n-d))

a(n)=local(A); A=exp(sum(k=1, n, 2*A090879(k)*x^k/k)+x*O(x^n)); polcoeff(A, n)

for(n=0, 30, print1(a(n), ", ")) \\ Paul D. Hanna, Jan 05 2014

CROSSREFS

Cf. A110153, A110154, A110155, A110156.

Sequence in context: A025257 A283438 A323027 * A245560 A175654 A017922

Adjacent sequences:  A110149 A110150 A110151 * A110153 A110154 A110155

KEYWORD

nonn

AUTHOR

Paul D. Hanna, Jul 14 2005

STATUS

approved

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Last modified August 14 16:58 EDT 2022. Contains 356122 sequences. (Running on oeis4.)