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 A208120 #7 Jul 22 2025 21:10:54 %S A208120 12,144,420,1225,7315,43681,175560,705600,3503640,17397241,76934095, %T A208120 340218025,1602280260,7546049424,34331884092,156198057961, %U A208120 724234470091,3358015935121,15408300507600,70701190560000,326286103743600 %N A208120 Number of 5Xn 0..1 arrays avoiding 0 0 0 and 0 1 0 horizontally and 0 0 1 and 0 1 1 vertically. %C A208120 Row 5 of A208118 %H A208120 R. H. Hardin, <a href="/A208120/b208120.txt">Table of n, a(n) for n = 1..210</a> %F A208120 Empirical: a(n) = a(n-1) -6*a(n-2) +29*a(n-3) +247*a(n-4) +246*a(n-5) +1656*a(n-6) -9936*a(n-8) -8856*a(n-9) -53352*a(n-10) -37584*a(n-11) +46656*a(n-12) -46656*a(n-13) +279936*a(n-14) %e A208120 Some solutions for n=4 %e A208120 ..1..0..1..1....1..0..1..1....0..1..1..0....0..1..1..1....1..0..0..1 %e A208120 ..1..1..0..1....1..0..0..1....0..1..1..1....0..0..1..1....0..1..1..0 %e A208120 ..0..0..1..1....1..0..0..1....0..1..1..0....0..1..1..1....1..0..0..1 %e A208120 ..1..0..0..1....1..0..0..1....0..0..1..1....0..0..1..1....0..1..1..0 %e A208120 ..0..0..1..1....1..0..0..1....0..1..1..0....0..1..1..1....1..0..0..1 %K A208120 nonn %O A208120 1,1 %A A208120 _R. H. Hardin_ Feb 23 2012