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 A278728 #7 Jun 09 2023 08:18:19 %S A278728 6,152,1947,17352,121520,712406,3633649,16547278,68531079,261693631, %T A278728 931194981,3113638802,9849622993,29642927267,85271613063,235393492799, %U A278728 625708778733,1606286648601,3992748071821,9631887926896,22595573914587 %N A278728 Number of n X 2 0..3 arrays with rows in nondecreasing lexicographic order and columns in nonincreasing lexicographic order, but with exactly one mistake. %C A278728 Column 2 of A278734. %H A278728 R. H. Hardin, <a href="/A278728/b278728.txt">Table of n, a(n) for n = 1..210</a> %H A278728 R. H. Hardin, <a href="/A278728/a278728.txt">Empirical polynomial of degree 28</a> %F A278728 Empirical polynomial of degree 28 (see link above). %e A278728 Some solutions for n=4 %e A278728 ..2..2. .1..1. .2..1. .1..1. .2..0. .1..0. .3..0. .0..0. .1..1. .2..2 %e A278728 ..3..0. .1..1. .2..2. .3..2. .3..2. .3..2. .3..0. .3..1. .2..1. .3..0 %e A278728 ..0..2. .0..0. .1..0. .2..2. .0..0. .0..0. .3..0. .1..0. .2..2. .2..3 %e A278728 ..0..2. .1..1. .1..0. .2..3. .2..0. .0..1. .2..1. .1..0. .1..0. .3..2 %Y A278728 Cf. A278734. %K A278728 nonn %O A278728 1,1 %A A278728 _R. H. Hardin_, Nov 27 2016