A035623 Number of partitions of n into parts 4k and 4k+3 with at least one part of each type.

0, 0, 0, 0, 0, 0, 1, 0, 0, 1, 3, 0, 1, 3, 6, 1, 3, 7, 12, 3, 7, 15, 21, 7, 16, 28, 36, 16, 31, 50, 60, 32, 57, 85, 98, 60, 100, 141, 157, 107, 169, 226, 248, 184, 276, 358, 385, 305, 442, 553, 591, 495, 691, 845, 896, 782, 1063, 1270, 1343, 1216, 1608, 1890, 1993

Offset: 1

Author

Olivier Gérard

Keywords

• nonn

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A035441-A035468, A035618-A035622, A035624-A035699.

Programs

Maple

N:= 100:
P:= (-1 + 1/mul(1-x^(4*k+3), k=0..(N-3)/4))*(-1 + 1/mul(1-x^(4*k), k=1..N/4)):
S:= series(P,x,N+1):
seq(coeff(S,x,j),j=1..N); # Robert Israel, Feb 23 2016

Mathematica

nmax = 63; s1 = Range[1, nmax/4]*4; s2 = Range[0, nmax/4]*4 + 3;
Table[Count[IntegerPartitions[n, All, s1~Join~s2],
x_ /; ContainsAny[x, s1 ] && ContainsAny[x, s2 ]], {n, 1, nmax}] (* Robert Price, Aug 06 2020 *)
nmax = 63; l = Rest@CoefficientList[Series[(-1 + 1/Product[(1 - x^(4 k + 3)), {k, 0, nmax}])*(-1 + 1/Product[(1 - x^(4 k)), {k, 1, nmax}]), {x, 0, nmax}], x]  (* Robert Price, Aug 06 2020 *)

Formula

G.f.: (-1 + 1/Product_{k>=0} (1-x^(4k+3)))*(-1 + 1/Product_{k>=1} (1-x^(4k))). - Robert Israel, Feb 23 2016

a(n) ~ exp(Pi*sqrt(n/3)) * Pi^(3/4) / (2^(5/4) * 3^(5/8) * Gamma(1/4) * n^(9/8)). - Vaclav Kotesovec, May 26 2018