A220675 - OEIS

%I #5 Dec 18 2015 18:18:24

%S 1,4,43,2024,468036,455249977,2045717834201,40852471994323068,

%T 3654942390444289784060

%N Number of ways to reciprocally link elements of an n X n array either to themselves or to exactly two horizontal, vertical and antidiagonal neighbors, without consecutive collinear links

%C Diagonal of A220681

%e Some solutions for n=3 0=self 2=n 3=ne 4=w 6=e 7=sw 8=s (reciprocal directions total 10)

%e .00.67.47...00.00.00...00.67.48...68.47.00...00.78.78...00.68.48...00.67.48

%e .38.36.47...00.78.00...38.00.27...23.00.00...38.23.27...68.24.27...36.48.27

%e .26.34.00...36.24.00...26.34.00...00.00.00...26.34.00...26.34.00...00.23.00

%K nonn

%O 1,2

%A _R. H. Hardin_ Dec 17 2012