A330658 Number of ways to place zero or more dominoes on an n X n grid with an equal number of horizontal and vertical dominoes.

1, 1, 1, 23, 1608, 371500, 328956227, 1126022690953, 14806761014366079, 744494518032208898560, 142687918961909575461700797, 103997384424546478979311463191760, 287748628673335369235353717267441839979, 3018422667417995172483450578913829739500058615

Offset: 0

Author

Andrew Howroyd, Mar 01 2020

Keywords

• nonn

Examples

			a(1) = a(2) = 1 because the only possibility is placing no dominoes at all.
a(3) = 23 because there is 1 way to place no dominoes, 20 ways to place one horizontal domino and one vertical domino, and 2 ways to place two horizontal and two vertical dominoes.
		

Crossrefs

Cf. A028420, A332714.