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 A206996 #7 Jul 22 2025 19:54:44 %S A206996 12,144,1011,6612,38144,211471,1124120,5856490,29993573,152063662, %T A206996 764940884,3828258995,19086321346,94907855054,471032090907, %U A206996 2334592278836,11559687446670,57197509727715,282871139080418,1398435823681688 %N A206996 Number of nX4 0..1 arrays avoiding 0 1 0 horizontally and 0 1 1 vertically. %C A206996 Column 4 of A207000 %H A206996 R. H. Hardin, <a href="/A206996/b206996.txt">Table of n, a(n) for n = 1..210</a> %F A206996 Empirical: a(n) = 10*a(n-1) -18*a(n-2) -96*a(n-3) +314*a(n-4) +205*a(n-5) -1435*a(n-6) +363*a(n-7) +2647*a(n-8) -1601*a(n-9) -2021*a(n-10) +1517*a(n-11) +728*a(n-12) -593*a(n-13) -121*a(n-14) +101*a(n-15) +7*a(n-16) -6*a(n-17) %e A206996 Some solutions for n=4 %e A206996 ..0..0..1..1....0..0..1..1....1..0..1..1....1..0..0..0....1..1..1..1 %e A206996 ..0..1..1..0....0..1..1..1....0..0..1..1....1..0..0..0....1..1..1..1 %e A206996 ..0..0..0..0....0..0..1..1....1..1..0..1....1..1..1..0....1..1..1..1 %e A206996 ..1..0..0..1....0..1..1..1....0..0..0..1....0..0..0..1....1..1..1..0 %K A206996 nonn %O A206996 1,1 %A A206996 _R. H. Hardin_ Feb 14 2012