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A330459
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Number of set partitions of set-systems with total sum n.
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10
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1, 1, 1, 4, 6, 11, 26, 42, 78, 148, 280, 481, 867, 1569, 2742, 4933, 8493, 14857, 25925, 44877, 77022, 132511, 226449, 385396, 657314, 1111115, 1875708, 3157379, 5309439, 8885889, 14861478, 24760339, 41162971, 68328959, 113099231, 186926116, 308230044
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OFFSET
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0,4
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COMMENTS
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Number of sets of disjoint nonempty sets of nonempty sets of positive integers with total sum n.
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LINKS
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FORMULA
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EXAMPLE
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The a(6) = 26 partitions:
((6)) ((15)) ((123)) ((1)(2)(12))
((24)) ((1)(14)) ((1))((2)(12))
((1)(5)) ((1)(23)) ((12))((1)(2))
((2)(4)) ((2)(13)) ((2))((1)(12))
((1))((5)) ((3)(12)) ((1))((2))((12))
((2))((4)) ((1))((14))
((1))((23))
((1)(2)(3))
((2))((13))
((3))((12))
((1))((2)(3))
((2))((1)(3))
((3))((1)(2))
((1))((2))((3))
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MATHEMATICA
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ppl[n_, k_]:=Switch[k, 0, {n}, 1, IntegerPartitions[n], _, Join@@Table[Union[Sort/@Tuples[ppl[#, k-1]&/@ptn]], {ptn, IntegerPartitions[n]}]];
Table[Length[Select[ppl[n, 3], And[UnsameQ@@Join@@#, And@@UnsameQ@@@Join@@#]&]], {n, 0, 10}]
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PROG
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L(n)={eta(x^2 + O(x*x^n))/eta(x + O(x*x^n))}
BellP(n)={serlaplace(exp( exp(x + O(x*x^n)) - 1))}
seq(n)={my(c=L(n), b=BellP(n), v=Vec(prod(k=1, n, (1 + x^k*y + O(x*x^n))^polcoef(c, k)))); vector(#v, n, my(r=v[n]); sum(k=0, n-1, polcoeff(b, k)*polcoef(r, k)))} \\ Andrew Howroyd, Dec 29 2019
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CROSSREFS
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Cf. A007713, A050342, A050343, A279375, A279785, A283877, A294617, A330460, A330462, A323787-A323795, A330452-A330459.
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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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