A171009 Number of ways to place two non-attacking queens on all free n-ominoes.

0, 0, 0, 2, 21, 131, 733, 3882, 19641, 97282

Offset

1,4

Links

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

Example

The pentomino XXXX admits 2 combinations of 2 non-attacking queens.
............. X

Crossrefs

Sequence in context: A091789 A109789 A136588 * A098661 A095262 A209519

Adjacent sequences: A171006 A171007 A171008 * A171010 A171011 A171012

Keyword

nonn

Author

David Scambler, Aug 27 2010

Status

approved