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 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

%I

%S 1,1,1,23,1608,371500,328956227,1126022690953,14806761014366079,

%T 744494518032208898560,142687918961909575461700797,

%U 103997384424546478979311463191760,287748628673335369235353717267441839979,3018422667417995172483450578913829739500058615

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

%e a(1) = a(2) = 1 because the only possibility is placing no dominoes at all.

%e 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.

%Y Cf. A028420, A332714.

%K nonn

%O 0,4

%A _Andrew Howroyd_, Mar 01 2020

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Last modified December 6 13:45 EST 2021. Contains 349563 sequences. (Running on oeis4.)