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 A206952 #7 Jul 22 2025 19:49:50 %S A206952 25,625,11804,218637,4107593,77359677,1455935650,27394495918, %T A206952 515466231841,9699443092866,182512279469866,3434286824366669, %U A206952 64622121983338176,1215978582236350201,22880768560680353074 %N A206952 Number of nX3 0..2 arrays avoiding the pattern z z+1 z in any row, column or nw-to-se diagonal. %C A206952 Column 3 of A206957 %H A206952 R. H. Hardin, <a href="/A206952/b206952.txt">Table of n, a(n) for n = 1..210</a> %e A206952 Some solutions for n=4 %e A206952 ..2..0..1....2..1..0....2..0..2....0..0..0....2..0..1....0..1..2....1..2..2 %e A206952 ..2..0..2....0..1..1....1..1..1....2..0..2....0..0..2....1..2..0....1..1..1 %e A206952 ..1..0..2....1..0..2....1..1..0....2..0..1....1..1..2....1..2..0....1..0..1 %e A206952 ..1..2..2....1..2..2....1..2..2....0..0..0....1..1..1....2..0..2....2..1..2 %K A206952 nonn %O A206952 1,1 %A A206952 _R. H. Hardin_ Feb 13 2012