A171010 Number of ways to place two non-attacking kings on all free n-ominoes.

0, 0, 1, 7, 46, 240, 1207, 6004, 28903, 137996

Offset

1,4

Links

Table of n, a(n) for n=1..10.

Example

E.g. the triomino XXX admits 1 combination of 2 non-attacking kings.

Crossrefs

Sequence in context: A175909 A034471 A100024 * A258630 A264201 A086092

Adjacent sequences: A171007 A171008 A171009 * A171011 A171012 A171013

Keyword

nonn

Author

David Scambler, Aug 27 2010

Status

approved