This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A275507 #8 Feb 04 2019 13:57:57 %S A275507 48,200,1168,7140,43780,268152,1643372,10069540,61703488,378096660, %T A275507 2316847540,14196847960,86993404476,533065762516,3266444015616, %U A275507 20015648328132,122649024958372,751551142797496,4605247533843404 %N A275507 Number of 7 X n 0..2 arrays with no element equal to any value at offset (-2,-1) (-2,0) or (-1,-1) and new values introduced in order 0..2. %H A275507 R. H. Hardin, <a href="/A275507/b275507.txt">Table of n, a(n) for n = 1..210</a> %F A275507 Empirical: a(n) = 3*a(n-1) + 18*a(n-2) + 11*a(n-3) - 23*a(n-4) - 4*a(n-5) for n>6. %F A275507 Empirical g.f.: 4*x*(12 + 14*x - 74*x^2 - 123*x^3 + 60*x^4 + 59*x^5) / (1 - 3*x - 18*x^2 - 11*x^3 + 23*x^4 + 4*x^5). - _Colin Barker_, Feb 04 2019 %e A275507 Some solutions for n=4: %e A275507 ..0..1..1..1. .0..1..1..2. .0..1..1..1. .0..0..1..1. .0..0..1..2 %e A275507 ..1..2..2..2. .1..1..2..0. .0..1..2..2. .1..1..2..2. .1..1..2..2 %e A275507 ..2..2..0..0. .2..2..2..0. .1..2..2..0. .2..2..2..0. .1..2..2..0 %e A275507 ..2..0..1..1. .2..0..0..1. .2..2..0..0. .2..0..0..0. .2..0..0..0 %e A275507 ..0..1..1..2. .0..0..1..1. .2..0..0..1. .0..1..1..1. .0..0..1..1 %e A275507 ..1..1..2..2. .0..1..1..2. .0..0..1..1. .0..1..2..2. .0..1..1..2 %e A275507 ..1..2..0..0. .1..2..2..2. .0..1..2..2. .2..2..0..0. .1..2..2..0 %Y A275507 Row 7 of A275504. %K A275507 nonn %O A275507 1,1 %A A275507 _R. H. Hardin_, Jul 30 2016