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 A217995 #8 Jul 23 2018 14:06:05 %S A217995 3,9,25,81,241,719,2181,6543,19623,58983,176995,531045,1593739, %T A217995 4781741,14346105,43041933,129130449,387399819,1162223437,3486708387, %U A217995 10460197183,31380761819,94142587347,282428344593,847286292987,2541861239481 %N A217995 Number of n X 1 arrays of the minimum or maximum value of corresponding elements and their horizontal and vertical neighbors in a random 0..2 n X 1 array. %C A217995 Column 1 of A217999. %H A217995 R. H. Hardin, <a href="/A217995/b217995.txt">Table of n, a(n) for n = 1..210</a> %F A217995 Empirical: a(n) = 3*a(n-1) + a(n-2) + 2*a(n-3) - 13*a(n-4) - 7*a(n-5) + 3*a(n-6). %F A217995 Empirical g.f.: x*(3 - 5*x^2 - 9*x^3 - 6*x^4 + 3*x^5) / ((1 - 3*x)*(1 - x^2 - 5*x^3 - 2*x^4 + x^5)). - _Colin Barker_, Jul 23 2018 %e A217995 Some solutions for n=3: %e A217995 ..1....2....0....0....2....1....1....1....2....1....0....2....2....0....2....1 %e A217995 ..0....2....2....2....2....2....2....1....0....1....2....0....2....0....1....0 %e A217995 ..1....2....0....1....1....0....2....2....2....0....2....0....0....1....2....0 %Y A217995 Cf. A217999. %K A217995 nonn %O A217995 1,1 %A A217995 _R. H. Hardin_, Oct 17 2012