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 A207601 #7 Jul 22 2025 20:37:43 %S A207601 8,64,168,441,1995,9025,30400,102400,403520,1590121,5746377,20766249, %T A207601 78708504,298321984,1101003640,4063425025,15221477315,57019231369, %U A207601 211813620480,786839961600,2936720666880,10960714625809,40800212085841 %N A207601 Number of 4Xn 0..1 arrays avoiding 0 0 0 and 0 1 0 horizontally and 0 0 1 and 1 0 1 vertically. %C A207601 Row 4 of A207599 %H A207601 R. H. Hardin, <a href="/A207601/b207601.txt">Table of n, a(n) for n = 1..210</a> %F A207601 Empirical: a(n) = a(n-1) -3*a(n-2) +16*a(n-3) +88*a(n-4) +72*a(n-5) +312*a(n-6) -936*a(n-8) -648*a(n-9) -2376*a(n-10) -1296*a(n-11) +729*a(n-12) -729*a(n-13) +2187*a(n-14) %e A207601 Some solutions for n=4 %e A207601 ..0..1..1..0....1..0..0..1....1..1..0..0....0..1..1..1....1..0..0..1 %e A207601 ..0..0..1..1....1..0..1..1....0..0..1..1....0..1..1..1....0..1..1..0 %e A207601 ..0..0..1..1....1..0..1..1....0..0..1..1....0..0..1..1....0..1..1..0 %e A207601 ..0..0..1..1....0..0..1..1....0..0..1..1....0..0..1..1....0..1..1..0 %K A207601 nonn %O A207601 1,1 %A A207601 _R. H. Hardin_ Feb 19 2012