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 A278848 #6 Apr 21 2020 12:55:10 %S A278848 0,0,66,30772,9317846,4026240722,3637198028018,8472288445687482, %T A278848 56864856173457018228,1168082099198500119983316 %N A278848 Number of n X n 0..1 arrays with rows in nondecreasing lexicographic order and columns in nonincreasing lexicographic order, but with exactly three mistakes. %C A278848 Diagonal of A278855. %e A278848 Some solutions for n=4 %e A278848 ..1..1..1..0. .1..1..0..0. .1..0..1..1. .1..1..1..0. .1..1..1..0 %e A278848 ..1..0..1..1. .1..1..0..0. .0..1..1..0. .1..0..1..1. .1..1..0..1 %e A278848 ..0..0..0..0. .0..1..0..1. .0..0..0..1. .0..0..1..1. .1..0..0..1 %e A278848 ..1..0..1..0. .1..0..1..0. .0..1..1..1. .1..1..1..0. .0..1..1..1 %Y A278848 Cf. A278855. %K A278848 nonn %O A278848 1,3 %A A278848 _R. H. Hardin_, Nov 29 2016