A330459 Number of set partitions of set-systems with total sum n.

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

Offset

0,4

Comments

Number of sets of disjoint nonempty sets of nonempty sets of positive integers with total sum n.

Links

Andrew Howroyd, Table of n, a(n) for n = 0..500

Formula

a(n) = Sum_k A330462(n,k) * A000110(k).

Example

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))

Mathematica

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}]

Prog

(PARI) \\ here L is A000009 and BellP is A000110 as series.
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

Crossrefs

Cf. A007713, A050342, A050343, A279375, A279785, A283877, A294617, A330460, A330462, A323787-A323795, A330452-A330459.

Sequence in context: A363581 A219520 A336343 * A285994 A290651 A358913

Adjacent sequences: A330456 A330457 A330458 * A330460 A330461 A330462

Keyword

nonn

Author

Gus Wiseman, Dec 17 2019

Extensions

Terms a(18) and beyond from Andrew Howroyd, Dec 29 2019

Status

approved