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 A278630 #4 Nov 24 2016 10:20:35 %S A278630 15,3354,234484,10776210,387551595,11719632199,309971214338, %T A278630 7350438329498,158870607154260,3165150394868325,58584816738347925, %U A278630 1013219703287606525,16445858865221341430,251416530890380206352 %N A278630 Number of nX4 0..2 arrays with rows in nondecreasing lexicographic order and columns in nonincreasing lexicographic order, but with exactly two mistakes. %C A278630 Column 4 of A278634. %H A278630 R. H. Hardin, <a href="/A278630/b278630.txt">Table of n, a(n) for n = 1..210</a> %e A278630 Some solutions for n=2 %e A278630 ..2..0..1..0. .1..2..2..1. .1..1..2..0. .0..0..2..2. .2..0..2..1 %e A278630 ..0..0..1..2. .0..2..2..1. .1..1..1..2. .0..0..2..0. .0..0..1..2 %Y A278630 Cf. A278634. %K A278630 nonn %O A278630 1,1 %A A278630 _R. H. Hardin_, Nov 24 2016