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 A207859 #7 Jul 22 2025 20:53:59 %S A207859 10,100,370,1369,7289,38809,178088,817216,3976696,19351201,91961095, %T A207859 437019025,2096687880,10059287616,48075784344,229765876921, %U A207859 1099823682601,5264542102681,25183871849968,120471522306304,576445792593008 %N A207859 Number of 4Xn 0..1 arrays avoiding 0 0 0 and 0 1 0 horizontally and 0 1 0 and 1 0 1 vertically. %C A207859 Row 4 of A207858 %H A207859 R. H. Hardin, <a href="/A207859/b207859.txt">Table of n, a(n) for n = 1..210</a> %F A207859 Empirical: a(n) = 2*a(n-1) +30*a(n-3) +161*a(n-4) +45*a(n-5) +166*a(n-6) -749*a(n-7) -4860*a(n-8) -1352*a(n-9) +3048*a(n-10) +4635*a(n-11) +28540*a(n-12) +11318*a(n-13) -11422*a(n-14) -4202*a(n-15) -69991*a(n-16) -28677*a(n-17) +609*a(n-18) -20891*a(n-19) +65400*a(n-20) +5094*a(n-21) +7969*a(n-22) +10090*a(n-23) -24802*a(n-24) +1479*a(n-25) -2070*a(n-26) -1380*a(n-27) +3917*a(n-28) -350*a(n-29) -75*a(n-30) +41*a(n-31) -140*a(n-32) +16*a(n-33) +a(n-35) +a(n-36) %e A207859 Some solutions for n=4 %e A207859 ..1..0..0..1....1..0..0..1....0..1..1..0....0..0..1..1....1..1..0..1 %e A207859 ..1..0..1..1....0..1..1..0....0..1..1..1....1..0..0..1....0..0..1..1 %e A207859 ..0..0..1..1....0..1..1..0....1..0..1..1....1..1..0..1....0..0..1..1 %e A207859 ..0..0..1..1....1..1..1..1....1..0..1..1....1..1..0..1....1..0..1..1 %K A207859 nonn %O A207859 1,1 %A A207859 _R. H. Hardin_ Feb 21 2012