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 A207497 #7 Jul 22 2025 20:30:17 %S A207497 13,169,699,2942,14253,68745,343310,1714707,8658045,43808202, %T A207497 222697019,1134527403,5795073744,29653954449,152010652165, %U A207497 780332029484,4010975606113,20639771978707,106316035774240,548128063053109 %N A207497 Number of nX5 0..1 arrays avoiding 0 0 0 and 0 1 1 horizontally and 0 0 1 and 1 0 0 vertically. %C A207497 Column 5 of A207500 %H A207497 R. H. Hardin, <a href="/A207497/b207497.txt">Table of n, a(n) for n = 1..210</a> %F A207497 Empirical: a(n) = 13*a(n-1) -17*a(n-2) -407*a(n-3) +1361*a(n-4) +5048*a(n-5) -24757*a(n-6) -30088*a(n-7) +231328*a(n-8) +66085*a(n-9) -1314702*a(n-10) +224399*a(n-11) +4884111*a(n-12) -2047901*a(n-13) -12326395*a(n-14) +6862627*a(n-15) +21620699*a(n-16) -13538690*a(n-17) -26727847*a(n-18) +17354874*a(n-19) +23481642*a(n-20) -14973565*a(n-21) -14711868*a(n-22) +8790663*a(n-23) +6559254*a(n-24) -3492706*a(n-25) -2059830*a(n-26) +917580*a(n-27) +444862*a(n-28) -151484*a(n-29) -62872*a(n-30) +14112*a(n-31) +5224*a(n-32) -560*a(n-33) -192*a(n-34) for n>35 %e A207497 Some solutions for n=4 %e A207497 ..1..0..1..0..1....1..1..1..1..1....0..0..1..0..0....0..0..1..0..0 %e A207497 ..0..0..1..0..0....1..1..0..1..0....1..1..1..1..0....0..1..0..0..1 %e A207497 ..1..0..1..0..1....1..1..1..1..1....1..1..1..1..0....0..0..1..0..0 %e A207497 ..1..0..1..0..0....1..0..1..0..0....0..1..0..1..0....0..1..0..0..1 %K A207497 nonn %O A207497 1,1 %A A207497 _R. H. Hardin_ Feb 18 2012