A271609 - OEIS

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.

%I #8 Jun 15 2017 22:10:57

%S 1,3,17,307,7764,222936,18314708,5436984025,1549076843600,

%T 327785587238680,258598550473174218,937062960563484014011,

%U 2266270598091075686029983,2979993347333205027776950744,18769591152933109773812486076631,672356922734153057389479052479321305

%N 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.

%C Diagonal of A271617.

%e Some solutions for n=4

%e .....6........0........0........6........6........0........0........0

%e ....6.1......6.0......0.6......0.1......6.1......0.5......4.3......4.3

%e ...5.1.6....0.1.6....4.3.1....0.6.6....5.1.6....0.2.6....0.0.6....5.6.0

%e ..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

%e Element moves: 0=itself 1=nw 2=ne 3=w 4=e 5=sw 6=se, reciprocals total 7

%Y Cf. A271617.

%K nonn

%O 1,2

%A _R. H. Hardin_, Apr 10 2016

%E a(13)-a(16) from _Alois P. Heinz_, Jun 15 2017