A273657 Number of forests of labeled rooted trees of height at most 1, with n labels, seven of which are used for root nodes and any root may contain >= 1 labels.

877, 26104, 463212, 6409320, 76595310, 832521096, 8480449692, 82506827832, 776400941745, 7128606776720, 64261876786536, 571350882111984, 5026991629995036, 43878686837771760, 380672326962043560, 3287071510635218064, 28280022744131688519, 242602886107926614952

Offset

7,1

Links

Alois P. Heinz, Table of n, a(n) for n = 7..1000

Formula

E.g.f.: x^7/7! * Sum_{j=0..7} Stirling2(7,j)*exp(x)^j.

a(n) = C(n,7) * Sum_{j=0..7} Stirling2(7,j) * j^(n-7).

Maple

a:= n-> binomial(n, 7)*add(Stirling2(7, j)*j^(n-7), j=0..7):
seq(a(n), n=7..40);

Crossrefs

Column k=7 of A143396.

Sequence in context: A294057 A255947 A048791 * A188391 A209464 A209526

Adjacent sequences: A273654 A273655 A273656 * A273658 A273659 A273660

Keyword

nonn

Author

Alois P. Heinz, May 27 2016

Status

approved