A363233 Number of partitions of n with rank a multiple of 4.
1, 0, 1, 1, 3, 1, 5, 4, 10, 8, 16, 17, 29, 29, 48, 53, 81, 89, 130, 149, 208, 238, 325, 381, 506, 592, 770, 910, 1165, 1374, 1738, 2057, 2571, 3038, 3761, 4451, 5461, 6447, 7855, 9270, 11219, 13214, 15899, 18703, 22386, 26276, 31306, 36691, 43525, 50902, 60149, 70221, 82679, 96325
Offset: 1
Keywords
Programs
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Maple
b:= proc(n, i, c) option remember; `if`(i>n, 0, `if`(i=n, `if`(irem(i-c, 4)=0, 1, 0), b(n-i, i, c+1)+b(n, i+1, c))) end: a:= n-> b(n, 1$2): seq(a(n), n=1..54); # Alois P. Heinz, May 23 2023
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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))))
Formula
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)).