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 A181215 #5 Jul 22 2025 08:36:05 %S A181215 16,256,2500,28561,337561,3857296,44408896,512750736,5909458129, %T A181215 68121522001,785456787600,9055597599504,104402987257284, %U A181215 1203692301444361,13877652596295601,159998643202876416,1844662908618342400 %N A181215 Number of nX4 binary matrices with no three 1's adjacent in a line diagonally or antidiagonally. %C A181215 Column 4 of A181217 %H A181215 R. H. Hardin, <a href="/A181215/b181215.txt">Table of n, a(n) for n=1..225</a> %F A181215 Empirical: a(n)=11*a(n-1)+16*a(n-2)-24*a(n-3)-906*a(n-4)-2624*a(n-5)+11414*a(n-6)+14042*a(n-7)+444*a(n-8)-92598*a(n-9)-52264*a(n-10)+100166*a(n-11)+77798*a(n-12)-14516*a(n-13)-50238*a(n-14)+950832*a(n-15)-91514*a(n-16)-1551794*a(n-17)-699816*a(n-18)+414094*a(n-19)+1438537*a(n-20)+72931*a(n-21)-647214*a(n-22)+142392*a(n-23)+31008*a(n-24)-44992*a(n-25)+6816*a(n-26)+2496*a(n-27)-256*a(n-28) %e A181215 Some avoided solutions for 3X4 %e A181215 ..1..1..0..0....1..0..1..0....0..0..0..1....0..0..0..1....1..0..0..0 %e A181215 ..0..0..1..0....0..1..0..0....1..0..1..0....0..0..1..0....0..1..0..0 %e A181215 ..0..0..0..1....0..0..1..0....0..1..0..0....0..1..1..0....0..1..1..0 %K A181215 nonn %O A181215 1,1 %A A181215 _R. H. Hardin_ Oct 10 2010