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 A274899 #6 Jan 01 2024 18:48:49 %S A274899 48,95,436,2049,9863,48269,237807,1173787,5803040,28746995,142599041, %T A274899 707620370,3511083299,17420351674,86438549422,428942623935, %U A274899 2128651136675,10563418237405,52420279346379,260132938554538,1290906088470552 %N A274899 Number of 7 X n 0..2 arrays with no element equal to any value at offset (0,-1) (-1,-1) or (-2,0) and new values introduced in order 0..2. %C A274899 Row 7 of A274895. %H A274899 R. H. Hardin, <a href="/A274899/b274899.txt">Table of n, a(n) for n = 1..210</a> %F A274899 Empirical: a(n) = 21*a(n-1) -209*a(n-2) +1330*a(n-3) -6059*a(n-4) +20839*a(n-5) -55739*a(n-6) +118287*a(n-7) -202495*a(n-8) +284119*a(n-9) -331806*a(n-10) +326718*a(n-11) -273224*a(n-12) +193798*a(n-13) -115270*a(n-14) +56258*a(n-15) -21837*a(n-16) +6481*a(n-17) -1404*a(n-18) +210*a(n-19) -20*a(n-20) +a(n-21) for n>22. %e A274899 Some solutions for n=4 %e A274899 ..0..1..0..1. .0..1..2..0. .0..1..2..1. .0..1..2..0. .0..1..0..1 %e A274899 ..0..2..0..2. .0..1..0..1. .0..2..0..1. .0..2..0..1. .1..2..0..1 %e A274899 ..1..2..1..2. .1..2..0..1. .1..2..1..2. .1..2..0..2. .2..0..1..2 %e A274899 ..2..0..1..0. .2..0..1..2. .2..0..1..2. .1..0..1..2. .0..1..2..0 %e A274899 ..0..1..2..0. .0..1..2..0. .2..0..2..0. .2..0..1..0. .1..2..0..1 %e A274899 ..1..2..0..1. .1..2..0..1. .0..1..2..1. .2..1..2..0. .2..0..1..2 %e A274899 ..1..2..0..1. .1..2..0..2. .0..2..0..1. .0..1..0..1. .2..1..2..0 %Y A274899 Cf. A274895. %K A274899 nonn %O A274899 1,1 %A A274899 _R. H. Hardin_, Jul 10 2016