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 A217640 #6 Jul 22 2025 23:42:06 %S A217640 9,27,163,877,5119,29101,166193,949883,5424617,30992313,177045523, %T A217640 1011403721,5777856321,33007064639,188559321601,1077181452713, %U A217640 6153607089559,35153670287907,200822133317793,1147235248764407 %N A217640 Number of nX3 arrays of the minimum value of corresponding elements and their horizontal, vertical or antidiagonal neighbors in a random 0..2 nX3 array. %C A217640 Column 3 of A217645 %H A217640 R. H. Hardin, <a href="/A217640/b217640.txt">Table of n, a(n) for n = 1..71</a> %F A217640 Empirical: a(n) = 5*a(n-1) +3*a(n-2) +9*a(n-3) -10*a(n-4) -7*a(n-5) -166*a(n-6) -3*a(n-7) -122*a(n-8) -71*a(n-9) +165*a(n-10) +43*a(n-11) -43*a(n-12) -7*a(n-13) +3*a(n-14) for n>15 %e A217640 Some solutions for n=3 %e A217640 ..0..0..2....0..0..0....1..0..0....0..0..1....0..0..0....0..0..2....0..0..0 %e A217640 ..0..1..2....0..0..0....1..0..0....0..1..2....0..0..0....0..1..1....0..0..0 %e A217640 ..1..2..2....1..2..2....0..0..0....2..2..2....0..1..2....1..1..1....2..0..0 %K A217640 nonn %O A217640 1,1 %A A217640 _R. H. Hardin_ Oct 09 2012