A035696 Number of partitions of n into parts 8k+4 and 8k+7 with at least one part of each type.
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, 1, 3, 0, 0, 1, 3, 0, 1, 3, 6, 0, 1, 3, 7, 1, 3, 7, 11, 1, 3, 8, 14, 3, 7, 14, 20, 3, 8, 17, 26, 7, 15, 27, 34, 8, 18, 34, 45, 15, 30, 48, 57, 18, 37, 61, 75, 31, 55, 83, 94, 38, 69, 106, 123, 58, 98, 139, 152, 72, 123, 177, 197, 105
Offset: 1
Keywords
Links
- Alois P. Heinz, Table of n, a(n) for n = 1..5000
Programs
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Mathematica
nmax = 80; s1 = Range[0, nmax/8]*8 + 4; s2 = Range[0, nmax/8]*8 + 7; Table[Count[IntegerPartitions[n, All, s1~Join~s2], x_ /; ContainsAny[x, s1 ] && ContainsAny[x, s2 ]], {n, 1, nmax}] (* Robert Price, Aug 16 2020 *) nmax = 80; l = Rest@CoefficientList[Series[(-1 + 1/Product[(1 - x^(8 k + 4)), {k, 0, nmax}])*(-1 + 1/Product[(1 - x^(8 k + 7)), {k, 0, nmax}]), {x, 0, nmax}], x] (* Robert Price, Aug 16 2020*)
Formula
G.f.: (-1 + 1/Product_{k>=0} (1 - x^(8 k + 4)))*(-1 + 1/Product_{k>=0} (1 - x^(8 k + 7))). - Robert Price, Aug 16 2020