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 A207407 #7 Jul 22 2025 20:23:07 %S A207407 14,196,966,4761,16284,55696,154580,429025,1033590,2490084,5404650, %T A207407 11730625,23481800,47004736,88175016,165405321,294131070,523036900, %U A207407 889299950,1512043225,2474485860,4049540496,6412154268,10153182169 %N A207407 Number of 7Xn 0..1 arrays avoiding 0 0 1 and 0 1 1 horizontally and 0 0 1 and 1 1 0 vertically. %C A207407 Row 7 of A207403 %H A207407 R. H. Hardin, <a href="/A207407/b207407.txt">Table of n, a(n) for n = 1..210</a> %F A207407 Empirical: a(n) = 2*a(n-1) +12*a(n-2) -26*a(n-3) -65*a(n-4) +156*a(n-5) +208*a(n-6) -572*a(n-7) -429*a(n-8) +1430*a(n-9) +572*a(n-10) -2574*a(n-11) -429*a(n-12) +3432*a(n-13) -3432*a(n-15) +429*a(n-16) +2574*a(n-17) -572*a(n-18) -1430*a(n-19) +429*a(n-20) +572*a(n-21) -208*a(n-22) -156*a(n-23) +65*a(n-24) +26*a(n-25) -12*a(n-26) -2*a(n-27) +a(n-28) %e A207407 Some solutions for n=4 %e A207407 ..1..0..0..0....0..0..0..0....0..1..0..0....1..1..0..0....1..0..1..0 %e A207407 ..0..1..0..0....1..0..1..0....0..1..0..1....1..1..0..0....1..1..0..1 %e A207407 ..0..1..0..0....0..0..0..0....0..1..0..1....1..1..0..0....1..1..0..1 %e A207407 ..0..1..0..0....0..0..0..0....0..1..0..1....1..1..0..0....1..1..0..1 %e A207407 ..0..1..0..0....0..0..0..0....0..1..0..1....1..1..0..0....1..1..0..1 %e A207407 ..0..1..0..0....0..0..0..0....0..1..0..1....1..1..0..0....1..1..0..1 %e A207407 ..0..1..0..0....0..0..0..0....0..1..0..1....1..1..0..0....1..1..0..1 %K A207407 nonn %O A207407 1,1 %A A207407 _R. H. Hardin_ Feb 17 2012