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A221140
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Second-order spt function.
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7
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0, 1, 5, 15, 35, 75, 140, 259, 435, 735, 1155, 1841, 2765, 4200, 6125, 8975, 12731, 18179, 25235, 35180, 48055, 65681, 88299, 118895, 157690, 209230, 274510, 359779, 466970, 605740, 778860, 1000462, 1276044, 1624845, 2056355, 2598855, 3265851, 4097763, 5117350
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OFFSET
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1,3
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LINKS
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MATHEMATICA
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om[2, p_List] := Module[{pu, m, f}, pu = Union[p]; m = Length[pu]; f[j_] := Count[p, pu[[j]]]; Binomial[f[1] + 1, 3] + f[1] Sum[Binomial[f[j] + 1, 2], {j, 2, m}]];
spt[2, n_] := Sum[om[2, p], {p, IntegerPartitions[n]}];
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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