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 A278773 #4 Nov 28 2016 08:17:21 %S A278773 0,20,266,1972,10784,48501,189595,665212,2138149,6384894,17895624, %T A278773 47447755,119746565,289136007,670787381,1500673676,3247602855, %U A278773 6817025467,13912884597,27665820296,53701416899,101922145950,189427147850 %N A278773 Number of nX3 0..1 arrays with rows in nondecreasing lexicographic order and columns in nonincreasing lexicographic order, but with exactly two mistakes. %C A278773 Column 3 of A278778. %H A278773 R. H. Hardin, <a href="/A278773/b278773.txt">Table of n, a(n) for n = 1..210</a> %F A278773 Empirical: a(n) = (1/121645100408832000)*n^19 + (1/800296713216000)*n^18 + (193/2134124568576000)*n^17 + (1/241416806400)*n^16 + (173/1280987136000)*n^15 + (26111/7846046208000)*n^14 + (12107647/188305108992000)*n^13 + (354047/362125209600)*n^12 + (113721193/9656672256000)*n^11 + (12542321/109734912000)*n^10 + (1257109487/1379524608000)*n^9 + (1427797621/241416806400)*n^8 + (1397907414289/47076277248000)*n^7 + (598789045909/5884534656000)*n^6 + (543697174847/2615348736000)*n^5 + (191422487/1005903360)*n^4 - (3436687523/44108064000)*n^3 - (46017833/154378224)*n^2 - (3115337/19399380)*n %e A278773 Some solutions for n=4 %e A278773 ..0..0..1. .0..1..0. .1..1..0. .1..1..1. .0..1..1. .1..1..1. .1..0..1 %e A278773 ..0..0..1. .0..0..0. .0..1..0. .1..1..1. .1..0..0. .1..0..1. .1..0..0 %e A278773 ..1..0..1. .1..0..1. .0..1..1. .0..1..0. .0..0..0. .1..1..1. .1..0..0 %e A278773 ..0..0..1. .1..1..0. .1..1..0. .1..0..1. .1..1..1. .1..1..1. .1..1..1 %Y A278773 Cf. A278778. %K A278773 nonn %O A278773 1,2 %A A278773 _R. H. Hardin_, Nov 28 2016