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 A207253 #7 Jul 22 2025 20:12:52 %S A207253 14,196,966,5950,34608,207298,1231650,7328836,43552190,258926454, %T A207253 1539300960,9151641190,54407912390,323463778900,1923038207286, %U A207253 11432757777574,67969500563024,404089167742226,2402372140150290 %N A207253 Number of nX7 0..1 arrays avoiding 0 0 1 and 1 0 1 horizontally and 0 1 0 and 1 0 1 vertically. %C A207253 Column 7 of A207254 %H A207253 R. H. Hardin, <a href="/A207253/b207253.txt">Table of n, a(n) for n = 1..210</a> %F A207253 Empirical: a(n) = 4*a(n-1) +7*a(n-2) +4*a(n-3) +102*a(n-4) +156*a(n-5) +223*a(n-6) +518*a(n-7) +545*a(n-8) +578*a(n-9) +532*a(n-10) +306*a(n-11) +173*a(n-12) -124*a(n-13) -147*a(n-14) -50*a(n-15) -14*a(n-16) +22*a(n-17) +a(n-18) +2*a(n-19) -a(n-20) %e A207253 Some solutions for n=4 %e A207253 ..1..0..0..0..0..0..0....1..1..1..0..0..0..0....1..1..0..0..0..0..0 %e A207253 ..0..1..0..0..0..0..0....0..0..0..0..0..0..0....0..1..1..0..0..0..0 %e A207253 ..0..1..0..0..0..0..0....0..0..0..0..0..0..0....0..1..1..0..0..0..0 %e A207253 ..1..1..1..1..0..0..0....0..0..0..0..0..0..0....1..0..0..0..0..0..0 %K A207253 nonn %O A207253 1,1 %A A207253 _R. H. Hardin_ Feb 16 2012