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 A278730 #4 Nov 27 2016 07:14:31 %S A278730 155,17352,1410818,99992428,6410559865,374757577056,19983433877142, %T A278730 971720519011047,43159978267689118,1757375854436887414, %U A278730 65916636060336105608,2289699277183162173304,74046423246945148450929 %N A278730 Number of nX4 0..3 arrays with rows in nondecreasing lexicographic order and columns in nonincreasing lexicographic order, but with exactly one mistake. %C A278730 Column 4 of A278734. %H A278730 R. H. Hardin, <a href="/A278730/b278730.txt">Table of n, a(n) for n = 1..133</a> %e A278730 Some solutions for n=2 %e A278730 ..2..0..3..1. .2..0..2..2. .1..1..2..2. .3..0..3..2. .0..3..1..1 %e A278730 ..3..2..0..3. .2..2..2..1. .3..1..2..0. .3..1..0..1. .2..0..1..0 %Y A278730 Cf. A278734. %K A278730 nonn %O A278730 1,1 %A A278730 _R. H. Hardin_, Nov 27 2016