cp's OEIS Frontend

A363233 Number of partitions of n with rank a multiple of 4.

%I A363233 #22 May 23 2023 10:46:54
%S A363233 1,0,1,1,3,1,5,4,10,8,16,17,29,29,48,53,81,89,130,149,208,238,325,381,
%T A363233 506,592,770,910,1165,1374,1738,2057,2571,3038,3761,4451,5461,6447,
%U A363233 7855,9270,11219,13214,15899,18703,22386,26276,31306,36691,43525,50902,60149,70221,82679,96325
%N A363233 Number of partitions of n with rank a multiple of 4.
%F A363233 G.f.: (1/Product_{k>=1} (1-x^k)) * Sum_{k>=1} (-1)^(k-1) * x^(k*(3*k-1)/2) * (1-x^k) * (1+x^(4*k)) / (1-x^(4*k)).
%p A363233 b:= proc(n, i, c) option remember; `if`(i>n, 0, `if`(i=n,
%p A363233      `if`(irem(i-c, 4)=0, 1, 0), b(n-i, i, c+1)+b(n, i+1, c)))
%p A363233     end:
%p A363233 a:= n-> b(n, 1$2):
%p A363233 seq(a(n), n=1..54);  # _Alois P. Heinz_, May 23 2023
%o A363233 (PARI) my(N=60, x='x+O('x^N)); Vec(1/prod(k=1, N, 1-x^k)*sum(k=1, N, (-1)^(k-1)*x^(k*(3*k-1)/2)*(1-x^k)*(1+x^(4*k))/(1-x^(4*k))))
%Y A363233 Cf. A000041, A328988, A340601, A363237, A363238, A363239.
%K A363233 nonn
%O A363233 1,5
%A A363233 _Seiichi Manyama_, May 23 2023