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 A274748 #4 Jul 04 2016 10:18:16 %S A274748 32,448,7858,143634,2661918,49475642,920432562,17123659885, %T A274748 318581114142,5927090659144,110271727008501,2051571144042267, %U A274748 38168848457457660,710119627548581257,13211556323824865000,245796923794474296948 %N A274748 Number of nX7 0..2 arrays with no element equal to any value at offset (-1,-2) (0,-1) or (-1,0) and new values introduced in order 0..2. %C A274748 Column 7 of A274749. %H A274748 R. H. Hardin, <a href="/A274748/b274748.txt">Table of n, a(n) for n = 1..210</a> %F A274748 Empirical: a(n) = 21*a(n-1) -27*a(n-2) -407*a(n-3) +1614*a(n-4) -2305*a(n-5) +777*a(n-6) +1788*a(n-7) -2530*a(n-8) +1209*a(n-9) +56*a(n-10) -295*a(n-11) +115*a(n-12) -15*a(n-13) for n>15 %e A274748 Some solutions for n=4 %e A274748 ..0..1..0..2..1..2..1. .0..1..0..2..0..1..0. .0..1..0..2..0..2..1 %e A274748 ..1..0..1..0..2..0..2. .2..0..2..0..1..0..1. .2..0..1..0..1..0..2 %e A274748 ..2..1..0..1..0..2..0. .1..2..0..2..0..1..2. .0..1..0..2..0..2..0 %e A274748 ..1..2..1..0..1..0..2. .0..1..2..1..2..0..1. .2..0..2..0..2..0..2 %Y A274748 Cf. A274749. %K A274748 nonn %O A274748 1,1 %A A274748 _R. H. Hardin_, Jul 04 2016