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 A261633 Expansion of Product_{k>=0} (1+x^(3*k+1))^3. 1
 1, 3, 3, 1, 3, 9, 9, 6, 12, 18, 15, 21, 37, 36, 33, 55, 69, 66, 90, 117, 111, 136, 195, 204, 217, 294, 330, 342, 447, 531, 541, 657, 804, 839, 978, 1215, 1288, 1419, 1755, 1936, 2094, 2535, 2846, 3027, 3588, 4123, 4392, 5073, 5869, 6261, 7080 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS FORMULA a(n) ~ exp(Pi*sqrt(n/3)) / (2 * 3^(1/4) * n^(3/4)). MATHEMATICA nmax=50; CoefficientList[Series[Product[(1+x^(3*k+1))^3, {k, 0, nmax}], {x, 0, nmax}], x] CROSSREFS Cf. A261612, A261615, A261634. Sequence in context: A262220 A325254 A202252 * A277103 A120919 A032240 Adjacent sequences:  A261630 A261631 A261632 * A261634 A261635 A261636 KEYWORD nonn AUTHOR Vaclav Kotesovec, Aug 27 2015 STATUS approved

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Last modified May 7 16:00 EDT 2021. Contains 343652 sequences. (Running on oeis4.)