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 A207113 #7 Jul 22 2025 20:02:05 %S A207113 8,64,200,643,1835,4534,11511,27012,62814,144676,325111,733469, %T A207113 1635998,3639007,8091148,17910532,39681294,87775953,194044225, %U A207113 429056388,947971827,2094875648,4628499152,10225059546,22590584639,49903794405 %N A207113 Number of 4Xn 0..1 arrays avoiding 0 0 0 and 0 1 1 horizontally and 0 0 1 and 1 1 0 vertically. %C A207113 Row 4 of A207111 %H A207113 R. H. Hardin, <a href="/A207113/b207113.txt">Table of n, a(n) for n = 1..210</a> %F A207113 Empirical: a(n) = 2*a(n-1) +5*a(n-2) -4*a(n-3) -23*a(n-4) +4*a(n-5) +40*a(n-6) +19*a(n-7) -38*a(n-8) -28*a(n-9) -a(n-11) +13*a(n-12) +38*a(n-13) +15*a(n-14) -31*a(n-15) -24*a(n-16) -2*a(n-17) +9*a(n-18) +6*a(n-19) +6*a(n-20) -2*a(n-21) -3*a(n-22) -a(n-23) +a(n-24) %e A207113 Some solutions for n=4 %e A207113 ..1..1..1..1....1..1..0..1....1..0..0..1....0..0..1..0....1..1..0..1 %e A207113 ..1..1..1..1....0..0..1..0....1..0..0..1....0..0..1..0....1..0..1..0 %e A207113 ..1..1..1..1....0..1..0..1....1..0..0..1....0..0..1..0....1..0..0..1 %e A207113 ..1..1..1..1....0..0..1..0....1..0..0..1....0..0..1..0....1..0..0..1 %K A207113 nonn %O A207113 1,1 %A A207113 _R. H. Hardin_ Feb 15 2012