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 A225978 #6 Jul 23 2025 05:25:49 %S A225978 15,138,1178,9113,61808,361361,1825607,8065278,31631401,111785599, %T A225978 360788468,1075829429,2993017696,7832960008,19417916324,45865067963, %U A225978 103734768130,225619306783,473616394498,962612525277,1899542726132 %N A225978 Number of nX4 binary arrays whose sum with another nX4 binary array containing no more than two 1s has rows and columns in lexicographically nondecreasing order. %C A225978 Column 4 of A225982 %H A225978 R. H. Hardin, <a href="/A225978/b225978.txt">Table of n, a(n) for n = 1..76</a> %F A225978 Empirical: a(n) = (23/14820309504000)*n^17 + (397/2615348736000)*n^16 + (1429/217945728000)*n^15 + (21083/130767436800)*n^14 + (156407/62270208000)*n^13 + (375707/14370048000)*n^12 + (3136061/16765056000)*n^11 + (21563/22861440)*n^10 + (26402329/6096384000)*n^9 + (423919927/18289152000)*n^8 + (68634593/598752000)*n^7 + (144700261/1437004800)*n^6 + (19312991563/12108096000)*n^5 - (22496273857/4540536000)*n^4 + (97668459683/3027024000)*n^3 - (41460631/700700)*n^2 + (20134601/291720)*n - 23 for n>2 %e A225978 Some solutions for n=3 %e A225978 ..0..0..0..1....0..0..1..1....0..0..1..1....0..0..0..1....0..0..0..1 %e A225978 ..0..1..0..1....0..0..0..0....1..0..0..0....1..1..1..0....0..0..0..1 %e A225978 ..1..0..1..1....1..0..0..1....0..0..0..1....0..1..0..0....1..1..0..1 %K A225978 nonn %O A225978 1,1 %A A225978 _R. H. Hardin_ May 22 2013