A087648 a(n) = (1/2)*(Bell(n+2)+Bell(n+1)-Bell(n)).

1, 3, 9, 31, 120, 514, 2407, 12205, 66491, 386699, 2388096, 15589732, 107165081, 773106715, 5836100685, 45981026703, 377230766908, 3215977070706, 28437411817135, 260380616093533, 2464930698184351, 24091925888687459, 242802079705721156, 2520198597834860148

Offset

0,2

Comments

Sum of last number in all set partitions of n+1. E.g. The set partitions of 3 are {1,1,1}, {1,1,2}, {1,2,1}, {1,2,2} and {1,2,3}, so a(2) = 1+2+1+2+3 = 9. - Franklin T. Adams-Watters, Jun 07 2006

Number of partitions of the (n+2)-multiset {0,0,1,2,...,n} into distinct multisets. Also number of factorizations of 2 * Product_{i=1..n+1} prime(i) into distinct factors. - Alois P. Heinz, Jul 30 2021

Links

Vincenzo Librandi, Table of n, a(n) for n = 0..200

Mathematica

f[0]=1; f[n_] := Sum[ StirlingS2[n, k]*Binomial[k+2, k ], {k, 1, n}]; Table[ f[n], {n, 0, 20}] (* Zerinvary Lajos, Mar 31 2007 *)
(#[[3]]+#[[2]]-#[[1]])/2&/@Partition[BellB[Range[0, 30]], 3, 1] (* Harvey P. Dale, Jul 20 2021 *)

Prog

(Magma) [(1/2)*(Bell(n+2)+Bell(n+1)-Bell(n)) : n in [0..30]]; // Vincenzo Librandi, Nov 13 2011

Crossrefs

Cf. A000110, A035098, A059606.

Main diagonal of A120057, row sums of A120095.

Column 1 of array in A322770.

Row n=2 of A346520.

Sequence in context: A371724 A377954 A066571 * A086616 A040027 A182968

Adjacent sequences: A087645 A087646 A087647 * A087649 A087650 A087651

Keyword

nonn

Author

Vladeta Jovovic, Sep 23 2003

Status

approved