A271609 Number of ways to reciprocally link elements of an n X n X n triangular array with themselves or a neighbor, with no more than n elements linked to themselves.

1, 3, 17, 307, 7764, 222936, 18314708, 5436984025, 1549076843600, 327785587238680, 258598550473174218, 937062960563484014011, 2266270598091075686029983, 2979993347333205027776950744, 18769591152933109773812486076631, 672356922734153057389479052479321305

Offset: 1

Author

R. H. Hardin, Apr 10 2016

Keywords

• nonn

Comments

Diagonal of A271617.

Examples

			Some solutions for n=4
.....6........0........0........6........6........0........0........0
....6.1......6.0......0.6......0.1......6.1......0.5......4.3......4.3
...5.1.6....0.1.6....4.3.1....0.6.6....5.1.6....0.2.6....0.0.6....5.6.0
..2.4.3.1..4.3.0.1..0.4.3.0..0.0.1.1..2.0.0.1..4.3.0.1..4.3.0.1..2.0.1.0
Element moves: 0=itself 1=nw 2=ne 3=w 4=e 5=sw 6=se, reciprocals total 7
		

Crossrefs

Cf. A271617.

Extensions

a(13)-a(16) from Alois P. Heinz, Jun 15 2017