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 A278849 #4 Nov 29 2016 10:22:58 %S A278849 0,0,1,25,239,1486,7072,27828,94720,287298,793024,2023332,4828941, %T A278849 10881820,23327332,47861324,94458120,180072500,332769135,597905471, %U A278849 1047219371,1791963626,3001600740,4930040800,7951993320,12612734550 %N A278849 Number of nX2 0..1 arrays with rows in nondecreasing lexicographic order and columns in nonincreasing lexicographic order, but with exactly three mistakes. %C A278849 Column 2 of A278855. %H A278849 R. H. Hardin, <a href="/A278849/b278849.txt">Table of n, a(n) for n = 1..210</a> %F A278849 Empirical: a(n) = (1/87178291200)*n^14 + (1/958003200)*n^13 + (43/958003200)*n^12 + (893/958003200)*n^11 + (863/87091200)*n^10 + (11/358400)*n^9 + (28333/609638400)*n^8 + (32029/87091200)*n^7 + (13219/21772800)*n^6 - (119603/10886400)*n^5 - (291547/59875200)*n^4 + (883781/19958400)*n^3 + (127307/30270240)*n^2 - (467/13860)*n %e A278849 Some solutions for n=4 %e A278849 ..1..1. .1..1. .0..1. .0..1. .1..1. .0..1. .1..1. .1..1. .1..1. .0..0 %e A278849 ..0..1. .0..1. .1..1. .0..0. .0..0. .1..1. .0..1. .0..1. .1..0. .1..1 %e A278849 ..1..0. .0..0. .1..0. .1..1. .0..1. .0..1. .1..1. .1..1. .0..1. .0..1 %e A278849 ..0..1. .1..1. .0..1. .0..1. .0..0. .0..0. .0..0. .1..0. .0..0. .0..0 %Y A278849 Cf. A278855. %K A278849 nonn %O A278849 1,4 %A A278849 _R. H. Hardin_, Nov 29 2016