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 A207217 #7 Jul 22 2025 20:08:30 %S A207217 69,4761,247163,12584703,647820815,33403462497,1721695415743, %T A207217 88730578258613,4572950799187243,235680064764200747, %U A207217 12146435820476346225,626000438753879535467,32262680221309448337639,1662747377281516450070519 %N A207217 Number of nX4 0..2 arrays avoiding the pattern z z+1 z in any row or column. %C A207217 Column 4 of A207221 %H A207217 R. H. Hardin, <a href="/A207217/b207217.txt">Table of n, a(n) for n = 1..210</a> %e A207217 Some solutions for n=4 %e A207217 ..0..2..0..1....0..2..0..2....1..2..2..2....2..0..0..0....2..2..2..1 %e A207217 ..2..0..1..1....2..2..0..2....1..2..2..2....0..1..1..0....2..1..0..2 %e A207217 ..0..2..1..1....2..0..1..2....1..2..2..1....0..1..1..2....2..0..0..2 %e A207217 ..2..0..0..1....0..2..1..0....1..2..2..1....2..2..0..1....1..0..1..2 %K A207217 nonn %O A207217 1,1 %A A207217 _R. H. Hardin_ Feb 16 2012