# Greetings from The On-Line Encyclopedia of Integer Sequences! http://oeis.org/ Search: id:a193809 Showing 1-1 of 1 %I A193809 #5 Dec 18 2015 18:17:43 %S A193809 5,52,496,7536,224792,13949968,1780090736,465161983824, %T A193809 246624000644912,263286800959827832,563752320057171922352, %U A193809 2417354884909931307656688,20747077497647444504550311672 %N A193809 Number of n X n symmetric 0..4 arrays with no element equal to the difference mod 5 of any two of its horizontal and vertical neighbors %e A193809 Some solutions for 4X4 %e A193809 ..1..2..2..1....3..4..1..4....3..2..4..4....1..4..3..3....3..2..3..2 %e A193809 ..2..2..1..2....4..3..4..3....2..3..2..4....4..3..4..3....2..3..3..2 %e A193809 ..2..1..2..2....1..4..3..3....4..2..3..2....3..4..3..3....3..3..2..3 %e A193809 ..1..2..2..2....4..3..3..2....4..4..2..3....3..3..3..3....2..2..3..1 %K A193809 nonn %O A193809 1,1 %A A193809 _R. H. Hardin_ Aug 05 2011 # Content is available under The OEIS End-User License Agreement: http://oeis.org/LICENSE