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 A278721 #5 Nov 27 2016 06:46:20 %S A278721 10,60,275,1050,3492,10401,28288,71266,168155,374868,795158,1614184, %T A278721 3151188,5939970,10848924,19256291,33301148,56236656,92919425, %U A278721 150477730,239211960,373793355,574842060,870983100,1301499381,1919724600 %N A278721 Number of nX2 0..3 arrays with rows in nondecreasing lexicographic order and columns in nonincreasing lexicographic order. %C A278721 Column 2 of A278727. %H A278721 R. H. Hardin, <a href="/A278721/b278721.txt">Table of n, a(n) for n = 1..210</a> %F A278721 Empirical: a(n) = (1/479001600)*n^12 + (1/7257600)*n^11 + (1/248832)*n^10 + (103/1451520)*n^9 + (12631/14515200)*n^8 + (2663/345600)*n^7 + (433049/8709120)*n^6 + (342073/1451520)*n^5 + (1269197/1555200)*n^4 + (3605419/1814400)*n^3 + (521131/166320)*n^2 + (997/360)*n + 1 %e A278721 Some solutions for n=4 %e A278721 ..2..0. .0..0. .1..0. .1..0. .2..0. .1..0. .1..0. .0..0. .1..0. .0..0 %e A278721 ..2..1. .2..1. .1..0. .3..1. .2..1. .2..3. .3..0. .3..1. .1..0. .2..1 %e A278721 ..2..1. .2..1. .2..2. .3..1. .3..0. .3..2. .3..2. .3..3. .1..3. .3..1 %e A278721 ..3..1. .3..2. .2..3. .3..3. .3..3. .3..3. .3..3. .3..3. .1..3. .3..3 %Y A278721 Cf. A278727. %K A278721 nonn %O A278721 1,1 %A A278721 _R. H. Hardin_, Nov 27 2016