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Generating function Sum_{n >= 1} a(n)*x^n = Sum_{k>=1} k*x^(k*(3*k+1)/2)/(1-x^k).
4

%I #20 Dec 04 2020 04:22:31

%S 0,0,1,1,1,1,1,3,1,3,1,3,1,3,1,6,1,3,4,3,1,6,1,3,4,3,5,6,1,3,8,3,1,6,

%T 5,3,4,3,5,6,6,3,8,3,1,11,5,3,4,3,10,6,1,3,8,8,1,12,5,3,9,3,5,12,1,8,

%U 8,3,1,12,10,3,4,3,5,17,1,10,8,3,6,12,5,3,11,8,5,12,1,3

%N Generating function Sum_{n >= 1} a(n)*x^n = Sum_{k>=1} k*x^(k*(3*k+1)/2)/(1-x^k).

%C The OEIS contains many very similar sequences, but this one was missing.

%H Seiichi Manyama, <a href="/A338730/b338730.txt">Table of n, a(n) for n = 0..10000</a>

%o (PARI) my(N=66, x='x+O('x^N)); concat([0, 0], Vec(sum(k=1, N, k*x^(k*(3*k+1)/2)/(1-x^k)))) \\ _Seiichi Manyama_, Dec 03 2020

%Y Cf. A001227, A081757, A117277, A330889, A338731, A338732.

%K nonn

%O 0,8

%A _N. J. A. Sloane_, Dec 02 2020