A215764 Number of undirected labeled graphs on n nodes with exactly 4 cycle graphs as connected components.

1, 10, 65, 420, 3157, 27342, 264925, 2831455, 33077539, 419262987, 5730379473, 84009491475, 1315019717433, 21890336017248, 386143234692768, 7195289865439824, 141228388872794736, 2912462945497687680, 62959048637195335680, 1423638554827333204800

Offset

4,2

Links

Alois P. Heinz, Table of n, a(n) for n = 4..175

Example

a(4) = 1:  o1.2o
.          .....
.          o3.4o

Maple

T:= proc(n, k) option remember; `if`(k<0 or k>n, 0, `if`(n=0, 1,
      add(binomial(n-1, i)*T(n-1-i, k-1)*ceil(i!/2), i=0..n-k)))
    end:
a:= n-> T(n, 4):
seq (a(n), n=4..25);

Crossrefs

Column k=4 of A215771.

Sequence in context: A097791 A212259 A198848 * A262342 A307144 A344047

Adjacent sequences: A215761 A215762 A215763 * A215765 A215766 A215767

Keyword

nonn

Author

Alois P. Heinz, Aug 23 2012

Status

approved