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A266944 Expansion of Product_{k>=1} 1 / (1 - 3*x^k))^2. 2
1, 6, 33, 150, 636, 2508, 9501, 34674, 123369, 429396, 1469733, 4959600, 16545597, 54662046, 179124837, 582893052, 1885479918, 6067245570, 19435083054, 62006825166, 197128631562, 624716063502, 1974151076946, 6222482535642, 19567579430643, 61403207075448 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

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

FORMULA

a(n) ~ c * n * 3^n, where c = Product_{k>=1} 1/(1-1/3^k)^2 = 1/QPochhammer(1/3)^2 = 3.187340158492291107944103748176139... .

MATHEMATICA

nmax = 40; CoefficientList[Series[Product[1/(1-3*x^k)^2, {k, 1, nmax}], {x, 0, nmax}], x]

CROSSREFS

Cf. A242587, A266943.

Sequence in context: A297592 A255613 A022730 * A301272 A290921 A240880

Adjacent sequences:  A266941 A266942 A266943 * A266945 A266946 A266947

KEYWORD

nonn

AUTHOR

Vaclav Kotesovec, Jan 06 2016

STATUS

approved

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Last modified October 20 11:09 EDT 2018. Contains 316379 sequences. (Running on oeis4.)