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 A206885 #7 Jul 22 2025 19:46:37 %S A206885 12,144,1103,7878,51800,330951,2070564,12830802,79045687,485544940, %T A206885 2977554668,18243896709,111730524932,684100356564,4188038973519, %U A206885 25637266851722,156933921465968,960624347689059,5880116589637756 %N A206885 Number of nX4 0..1 arrays avoiding 0 1 0 horizontally and 1 0 0 vertically. %C A206885 Column 4 of A206889 %H A206885 R. H. Hardin, <a href="/A206885/b206885.txt">Table of n, a(n) for n = 1..210</a> %F A206885 Empirical: a(n) = 11*a(n-1) -14*a(n-2) -193*a(n-3) +496*a(n-4) +1310*a(n-5) -4382*a(n-6) -4486*a(n-7) +18762*a(n-8) +8132*a(n-9) -44696*a(n-10) -6382*a(n-11) +61529*a(n-12) -2253*a(n-13) -48436*a(n-14) +8149*a(n-15) +20392*a(n-16) -5560*a(n-17) -3842*a(n-18) +1352*a(n-19) +192*a(n-20) -80*a(n-21) %e A206885 Some solutions for n=4 %e A206885 ..0..0..0..1....1..0..0..1....1..0..1..1....1..0..0..1....0..1..1..0 %e A206885 ..1..0..1..1....0..1..1..0....1..1..0..0....1..0..0..0....0..0..1..1 %e A206885 ..0..0..1..1....1..1..0..1....1..1..1..1....1..1..1..1....0..1..1..1 %e A206885 ..1..1..0..0....1..0..1..1....1..0..1..1....1..0..1..1....1..0..0..0 %K A206885 nonn %O A206885 1,1 %A A206885 _R. H. Hardin_ Feb 13 2012