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A035630
Number of partitions of n into parts 5k and 5k+4 with at least one part of each type.
3
0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 1, 3, 0, 0, 1, 3, 6, 0, 1, 3, 7, 11, 1, 3, 7, 14, 19, 3, 7, 15, 26, 32, 7, 15, 29, 46, 51, 15, 30, 53, 76, 81, 30, 56, 91, 124, 126, 57, 98, 152, 195, 195, 101, 167, 245, 304, 296, 174, 274, 388, 461, 448, 289, 441, 598, 696, 668, 470
OFFSET
1,14
LINKS
FORMULA
G.f.: (-1 + 1/Product_{k>=0} (1-x^(5k+4)))*(-1 + 1/Product_{k>=1} (1-x^(5k))). - Robert Price, Aug 07 2020
MATHEMATICA
nmax = 70; s1 = Range[1, nmax/5]*5; s2 = Range[0, nmax/5]*5 + 4;
Table[Count[IntegerPartitions[n, All, s1~Join~s2],
x_ /; ContainsAny[x, s1 ] && ContainsAny[x, s2 ]], {n, 1, nmax}] (* Robert Price, Aug 06 2020 *)
nmax = 70; l = Rest@CoefficientList[Series[(-1 + 1/Product[(1 - x^(5 k)), {k, 1, nmax}])*(-1 + 1/Product[(1 - x^(5 k + 4)), {k, 0, nmax}]), {x, 0, nmax}], x] (* Robert Price, Aug 06 2020 *)
KEYWORD
nonn
STATUS
approved