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A279281 Expansion of Product_{k>=1} (1 + x^(k*(3*k-2))). 7

%I #9 Apr 21 2017 04:39:03

%S 1,1,0,0,0,0,0,0,1,1,0,0,0,0,0,0,0,0,0,0,0,1,1,0,0,0,0,0,0,1,1,0,0,0,

%T 0,0,0,0,0,0,1,1,0,0,0,0,0,0,1,1,0,0,0,0,0,0,0,0,0,0,0,1,1,0,0,1,1,0,

%U 0,1,1,0,0,1,1,0,0,0,0,0,0,0,0,0,0,0,1,1,0,0,0,0,0,0,1,1,1,1,0,0,0,0,0,0,1,2,1,0,0,0,0,0,0,1,1,0,0,1,1

%N Expansion of Product_{k>=1} (1 + x^(k*(3*k-2))).

%C Number of partitions of n into distinct octagonal numbers (A000567).

%H G. C. Greubel, <a href="/A279281/b279281.txt">Table of n, a(n) for n = 0..1000</a>

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/OctagonalNumber.html">Octagonal Number</a>

%H <a href="/index/Pol#polygonal_numbers">Index to sequences related to polygonal numbers</a>

%H <a href="/index/Par#partN">Index entries for related partition-counting sequences</a>

%F G.f.: Product_{k>=1} (1 + x^(k*(3*k-2))).

%e a(105) = 2 because we have [96, 8, 1] and [65, 40].

%t nmax = 120; CoefficientList[Series[Product[1 + x^(k (3 k - 2)), {k, 1, nmax}], {x, 0, nmax}], x]

%Y Cf. A000567, A024940, A033461, A218380, A279041, A279279, A279280.

%K nonn

%O 0,106

%A _Ilya Gutkovskiy_, Dec 09 2016

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Last modified September 13 10:14 EDT 2024. Contains 375904 sequences. (Running on oeis4.)