cp's OEIS Frontend

A185560 1/4 the number of n X n 0..3 arrays with no element equal both to the element above and to the element to its left.

%I A185560 #9 Jul 22 2025 09:54:51
%S A185560 1,60,50580,598507920,99407416968000,231753101877188629380,
%T A185560 7583858300260627032845531520,3483475434832751291309593655505225600,
%U A185560 22459143127863154464679826472043109609252549520
%N A185560 1/4 the number of n X n 0..3 arrays with no element equal both to the element above and to the element to its left.
%C A185560 Diagonal of A185567
%H A185560 R. H. Hardin, <a href="/A185560/b185560.txt">Table of n, a(n) for n = 1..10</a>
%e A185560 Some solutions for 3X3 with a(1,1)=0
%e A185560 ..0..1..2....0..3..2....0..0..0....0..3..2....0..2..1....0..0..0....0..0..3
%e A185560 ..3..1..1....1..2..0....1..2..2....0..0..0....1..3..0....0..2..0....3..3..0
%e A185560 ..3..3..1....1..2..0....3..3..3....1..1..3....0..1..3....0..0..2....0..0..1
%K A185560 nonn
%O A185560 1,2
%A A185560 _R. H. Hardin_ Jan 31 2011