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 A203361 #7 Jul 22 2025 17:10:56 %S A203361 21,1640,89610,5390325,314688054,18550312526,1089970014327, %T A203361 64114204398028,3769915844080995,221699388876599524, %U A203361 13037021233036033635,766652822812020772883,45083423150083817466414,2651159090798112000786121 %N A203361 Number of nX7 binary arrays with every 1 immediately preceded by 0 to the left or above. %C A203361 Column 7 of A203362 %H A203361 R. H. Hardin, <a href="/A203361/b203361.txt">Table of n, a(n) for n = 1..210</a> %F A203361 Empirical: a(n) = 21*a(n-1) +1743*a(n-2) +25515*a(n-3) +156938*a(n-4) +213951*a(n-5) -1636533*a(n-6) -3128592*a(n-7) +23316551*a(n-8) +17066544*a(n-9) -199519590*a(n-10) +291472395*a(n-11) -22194350*a(n-12) -173766021*a(n-13) +129035841*a(n-14) -33578772*a(n-15) -2885164*a(n-16) +4086456*a(n-17) -689631*a(n-18) -24273*a(n-19) +4320*a(n-20) for n>21 %e A203361 Some solutions for n=3 %e A203361 ..0..1..0..0..1..0..0....0..0..0..0..0..1..0....0..0..1..0..1..0..1 %e A203361 ..0..0..1..0..0..1..1....0..1..0..0..0..1..1....0..0..1..0..1..0..1 %e A203361 ..0..1..0..1..0..1..0....1..0..1..1..0..1..0....1..1..0..1..0..0..1 %K A203361 nonn %O A203361 1,1 %A A203361 _R. H. Hardin_ Dec 31 2011