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 A251968 #7 Dec 29 2023 21:35:22 %S A251968 256,20000,6250000,1500625000,922368160000,410018473428480, %T A251968 371968759094317056,244967687215822061568,286806250077948918890496, %U A251968 248333886971163312349814784,348300471444720308054703841536 %N A251968 Number of (n+1) X (n+1) 0..3 arrays with nondecreasing sum of every two consecutive values in every row and column. %C A251968 Diagonal of A251974. %H A251968 R. H. Hardin, <a href="/A251968/b251968.txt">Table of n, a(n) for n = 1..12</a> %e A251968 Some solutions for n=2 %e A251968 ..3..2..3....1..0..2....1..0..1....2..1..2....1..0..2....1..0..1....0..0..1 %e A251968 ..0..1..0....0..1..3....3..0..3....2..1..3....1..1..1....2..2..3....0..3..1 %e A251968 ..3..2..3....1..3..3....1..3..1....3..3..3....3..3..3....3..1..3....2..3..2 %Y A251968 Cf. A251974. %K A251968 nonn %O A251968 1,1 %A A251968 _R. H. Hardin_, Dec 12 2014