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 A206870 #7 Jul 22 2025 19:45:16 %S A206870 81,6561,165783,4108471,115505069,3254925997,90497940567, %T A206870 2513905109615,69918135147567,1945015733467487,54104019551291657, %U A206870 1504951979516380911,41861310528949142861,1164403984942205341081,32388853771860099448897 %N A206870 Number of nX7 0..1 arrays avoiding 0 0 0 horizontally and 1 0 1 vertically. %C A206870 Column 7 of A206871 %H A206870 R. H. Hardin, <a href="/A206870/b206870.txt">Table of n, a(n) for n = 1..210</a> %e A206870 Some solutions for n=4 %e A206870 ..0..1..1..1..1..0..1....0..1..1..1..0..0..1....1..0..1..1..1..0..0 %e A206870 ..0..1..0..1..1..0..1....0..0..1..0..1..1..0....0..1..0..1..1..0..1 %e A206870 ..1..1..0..0..1..0..1....0..0..1..0..1..1..0....0..1..0..1..0..1..1 %e A206870 ..0..1..1..0..1..1..1....0..1..1..1..0..1..1....0..0..1..1..0..0..1 %K A206870 nonn %O A206870 1,1 %A A206870 _R. H. Hardin_ Feb 13 2012