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 A278434 #4 Nov 22 2016 06:55:20 %S A278434 1128,1287838,1796061464,2266913897519,2573951428892959, %T A278434 2817080307689646420,3058351651772615415451,3218514217113422076011068, %U A278434 3172598007779111848619027479,2870266355084730530696055472589 %N A278434 Number of nX6 0..3 arrays with rows and columns in lexicographic nondecreasing order but with exactly one mistake. %C A278434 Column 6 of A278435. %H A278434 R. H. Hardin, <a href="/A278434/b278434.txt">Table of n, a(n) for n = 1..18</a> %e A278434 Some solutions for n=1 %e A278434 ..0..1..2..3..1..3. .0..2..2..0..2..2. .3..3..1..1..1..3. .1..1..1..2..1..1 %Y A278434 Cf. A278435. %K A278434 nonn %O A278434 1,1 %A A278434 _R. H. Hardin_, Nov 22 2016