cp's OEIS Frontend

A198709 Number of n X n 0..3 arrays with values 0..3 introduced in row major order and no element equal to any horizontal or vertical neighbor.

%I A198709 #11 Jul 22 2025 13:05:18
%S A198709 1,4,401,250031,851787199,15835552812749,1606578861528554441,
%T A198709 889483369334451647489771,2687450673445984030296455830409
%N A198709 Number of n X n 0..3 arrays with values 0..3 introduced in row major order and no element equal to any horizontal or vertical neighbor.
%C A198709 Diagonal of A198715
%H A198709 Jean-François Alcover, <a href="/A198709/b198709.txt">Table of n, a(n) for n = 1..16</a>
%e A198709 Some solutions with all values from 0 to 3 for n=4
%e A198709 ..0..1..0..1....0..1..0..2....0..1..0..1....0..1..0..2....0..1..2..0
%e A198709 ..1..2..1..3....1..2..1..3....1..0..2..3....2..3..2..3....1..0..3..1
%e A198709 ..2..1..3..2....2..1..3..2....2..3..1..2....1..2..0..1....0..3..1..2
%e A198709 ..1..3..1..0....1..2..0..1....3..0..2..1....2..0..3..0....2..1..2..3
%t A198709 A198715 = Import["https://oeis.org/A198715/b198715.txt", "Table"][[All, 2]];
%t A198709 a[n_] := A198715[[2 n^2 - 2 n + 1]];
%t A198709 Table[a[n], {n, 1, 16}] (* _Jean-François Alcover_, Sep 23 2019 *)
%K A198709 nonn
%O A198709 1,2
%A A198709 _R. H. Hardin_ Oct 29 2011