A305106 - OEIS

A305106

Number of unitary factorizations of Heinz numbers of integer partitions of n. Number of multiset partitions of integer partitions of n with pairwise disjoint blocks.

1, 1, 2, 4, 7, 12, 21, 34, 55, 87, 138, 211, 324, 486, 727, 1079, 1584, 2305, 3337, 4789, 6830, 9712, 13689, 19225, 26841, 37322, 51598, 71108, 97580, 133350, 181558, 246335, 332991, 448706, 602607, 806732, 1077333, 1433885, 1903682, 2520246, 3328549, 4383929

(list; graph; refs; listen; history; text; internal format)

OFFSET

0,3

LINKS

Alois P. Heinz, Table of n, a(n) for n = 0..1000

EXAMPLE

The a(6) = 21 unitary factorizations:

(13) (21) (22) (25) (27) (28) (30) (36) (40) (48) (64)

(2*11) (2*15) (3*7) (3*10) (3*16) (4*7) (4*9) (5*6) (5*8)

(2*3*5)

The a(6) = 21 multiset partitions:

{{1},{5}}

{{1},{2,3}}

{{2},{4}}

{{2},{1,3}}

{{2},{1,1,1,1}}

{{1,1},{4}}

{{1,1},{2,2}}

{{3},{1,2}}

{{3},{1,1,1}}

{{1},{2},{3}}

MATHEMATICA

Table[Sum[BellB[Length[Union[y]]], {y, IntegerPartitions[n]}], {n, 30}]

(* Second program: *)

b[n_, i_, k_] := b[n, i, k] = If[n == 0, 1, If[i < 1, 0, Sum[With[{t = n - i j}, b[t, Min[t, i - 1], k]], {j, 1, n/i}] k + b[n, i - 1, k]]];

T[n_, k_] := Sum[b[n, n, k - i] (-1)^i Binomial[k, i], {i, 0, k}]/k!;

a[n_] := Sum[T[n, k], {k, 0, Floor[(Sqrt[1 + 8n] - 1)/2]}];

a /@ Range[0, 50] (* Jean-François Alcover, Dec 14 2020, after Alois P. Heinz in A321878 *)

CROSSREFS

Cf. A000110, A001055, A001221, A001970, A034444, A089233, A258466, A259936, A281116, A285572, A305078, A305079.

Row sums of A321878.

Sequence in context: A079816 A178937 A168368 * A182746 A100482 A301762

Adjacent sequences: A305103 A305104 A305105 * A305107 A305108 A305109

KEYWORD

nonn

AUTHOR

Gus Wiseman, May 25 2018

STATUS

approved