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 A204227 #7 Apr 20 2021 19:23:57 %S A204227 49284,2173565,87487117,2019310610,45791699846,687853333430, %T A204227 10297878073062,113754005579615,1254605391285859,10988697166912314, %U A204227 96030748646457765,701414832964037835,5107498255064984418 %N A204227 Number of (n+1) X 6 0..2 arrays with the sums of 2 X 2 subblocks nondecreasing rightwards and downwards. %C A204227 Column 5 of A204230. %H A204227 R. H. Hardin, <a href="/A204227/b204227.txt">Table of n, a(n) for n = 1..210</a> %e A204227 Some solutions for n=4 %e A204227 ..1..2..2..1..2..2....2..1..2..0..1..1....2..1..2..0..0..1....0..0..2..1..0..0 %e A204227 ..1..0..0..1..1..1....0..0..0..1..1..2....0..0..0..1..2..1....1..1..0..0..2..1 %e A204227 ..1..2..2..2..2..2....1..2..1..1..0..2....2..2..2..1..2..1....0..1..1..2..1..1 %e A204227 ..2..1..1..1..1..1....0..0..0..1..1..2....0..0..1..1..2..2....0..2..2..1..2..2 %e A204227 ..1..2..2..2..2..2....1..2..1..1..0..2....2..2..2..2..1..2....2..0..2..2..2..1 %Y A204227 Cf. A204230. %K A204227 nonn %O A204227 1,1 %A A204227 _R. H. Hardin_ Jan 13 2012