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 A278631 #4 Nov 24 2016 10:21:19 %S A278631 90,27521,3739008,387551595,33967584488,2593097277036,175644502146694, %T A278631 10734760074025367,600850493598843960,31181144570813141891, %U A278631 1514424057857433189463,69299571270775145840652 %N A278631 Number of nX5 0..2 arrays with rows in nondecreasing lexicographic order and columns in nonincreasing lexicographic order, but with exactly two mistakes. %C A278631 Column 5 of A278634. %H A278631 R. H. Hardin, <a href="/A278631/b278631.txt">Table of n, a(n) for n = 1..101</a> %e A278631 Some solutions for n=2 %e A278631 ..1..2..1..2..2. .1..1..1..0..2. .0..0..0..2..2. .0..0..0..0..2 %e A278631 ..2..2..2..1..0. .1..2..1..1..0. .0..0..2..2..1. .0..0..2..2..1 %Y A278631 Cf. A278634. %K A278631 nonn %O A278631 1,1 %A A278631 _R. H. Hardin_, Nov 24 2016