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 A278302 #6 Apr 21 2020 12:51:24 %S A278302 0,32,4558,2360544,6345491150,100825279690194,10174217016822816668, %T A278302 6850575319751106211878878 %N A278302 Number of n X n 0..2 arrays with rows and columns in lexicographic nondecreasing order but with exactly one mistake. %C A278302 Diagonal of A278309. %e A278302 Some solutions for n=3 %e A278302 ..1..2..1. .1..2..2. .1..2..2. .1..1..0. .0..0..1. .0..1..0. .0..0..0 %e A278302 ..2..0..0. .0..0..2. .2..1..2. .1..2..0. .1..0..1. .1..1..2. .1..0..2 %e A278302 ..2..0..2. .2..0..1. .0..1..0. .1..2..0. .2..0..1. .1..2..0. .1..1..1 %Y A278302 Cf. A278309. %K A278302 nonn %O A278302 1,2 %A A278302 _R. H. Hardin_, Nov 17 2016