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 A302273 #7 Apr 05 2018 04:09:53 %S A302273 1,7,22,79,269,942,3401,12283,43006,156939,565249,2007662,7307653, %T A302273 26305407,94096702,341521831,1229036517,4413205998,15980067713, %U A302273 57514505187,206942767678,748087603299,2693270343273,9700931065070 %N A302273 Number of n X 3 0..1 arrays with every element equal to 1, 2 or 4 horizontally, diagonally or antidiagonally adjacent elements, with upper left element zero. %C A302273 Column 3 of A302278. %H A302273 R. H. Hardin, <a href="/A302273/b302273.txt">Table of n, a(n) for n = 1..210</a> %F A302273 Empirical: a(n) = 2*a(n-1) +5*a(n-2) +26*a(n-3) -66*a(n-4) -86*a(n-5) +79*a(n-6) +14*a(n-7) +13*a(n-8) -168*a(n-9) +250*a(n-10) +428*a(n-11) -232*a(n-12) -24*a(n-13) -160*a(n-14) +160*a(n-15) -256*a(n-16) -384*a(n-17) +256*a(n-18). %e A302273 Some solutions for n=5: %e A302273 0 0 1 0 1 0 0 0 0 0 1 1 0 0 1 0 1 0 0 1 1 %e A302273 1 1 0 0 0 1 0 1 0 0 0 1 1 1 0 1 0 1 0 0 1 %e A302273 1 1 1 0 1 1 0 0 1 1 1 1 0 0 0 0 1 0 1 1 1 %e A302273 1 0 0 0 0 0 1 0 0 1 1 0 1 0 0 1 0 1 0 1 1 %e A302273 0 1 1 0 1 1 0 1 0 0 0 1 0 1 1 1 1 1 1 0 0 %Y A302273 Cf. A302278. %K A302273 nonn %O A302273 1,2 %A A302273 _R. H. Hardin_, Apr 04 2018