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 A207220 #7 Jul 22 2025 20:08:54 %S A207220 1465,2146225,1950327875,1721695415743,1547869995556777, %T A207220 1395037573042216457,1256433426475190769775,1131415114956594837875523, %U A207220 1018866149319377364919603291,917523154945563563526500635865 %N A207220 Number of nX7 0..2 arrays avoiding the pattern z z+1 z in any row or column. %C A207220 Column 7 of A207221 %H A207220 R. H. Hardin, <a href="/A207220/b207220.txt">Table of n, a(n) for n = 1..36</a> %e A207220 Some solutions for n=4 %e A207220 ..0..0..2..1..2..0..1....2..2..1..0..0..1..2....0..1..2..2..1..0..1 %e A207220 ..2..0..2..2..0..2..2....1..0..1..1..0..2..2....0..1..1..0..0..0..0 %e A207220 ..0..1..2..2..2..1..2....0..0..0..1..1..2..2....0..0..2..2..2..2..1 %e A207220 ..1..1..2..2..1..1..2....1..1..2..0..2..2..0....0..2..0..1..2..2..1 %K A207220 nonn %O A207220 1,1 %A A207220 _R. H. Hardin_ Feb 16 2012