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 A245991 #10 Nov 05 2018 21:03:11 %S A245991 64,208,676,2196,7132,23168,75260,244464,794096,2579500,8379052, %T A245991 27217860,88412560,287192948,932896352,3030352272,9843575108, %U A245991 31975148500,103865731612,337389844512,1095952482460,3560011839440,11564081956784 %N A245991 Number of length n+2 0..4 arrays with no pair in any consecutive three terms totalling exactly 4. %H A245991 R. H. Hardin, <a href="/A245991/b245991.txt">Table of n, a(n) for n = 1..210</a> %F A245991 Empirical: a(n) = 2*a(n-1) + a(n-2) + 9*a(n-3) + 3*a(n-4). %F A245991 Empirical g.f.: 4*x*(16 + 20*x + 49*x^2 + 15*x^3) / (1 - 2*x - x^2 - 9*x^3 - 3*x^4). - _Colin Barker_, Nov 05 2018 %e A245991 Some solutions for n=7: %e A245991 3 3 4 0 2 2 3 2 2 3 4 3 4 0 4 0 %e A245991 4 4 1 3 1 1 4 3 4 2 2 0 1 3 2 1 %e A245991 4 4 1 0 1 1 3 4 4 3 4 2 2 2 1 1 %e A245991 4 2 2 2 0 4 4 3 2 3 3 0 0 3 4 2 %e A245991 3 4 0 0 2 2 3 3 1 0 2 1 3 4 4 4 %e A245991 3 3 0 3 0 1 2 3 4 0 4 2 3 3 3 4 %e A245991 2 3 0 0 1 1 0 0 2 2 1 1 0 2 4 4 %e A245991 4 0 3 0 1 2 3 0 1 3 2 4 2 3 4 4 %e A245991 4 0 2 1 1 4 0 3 0 4 1 1 1 0 2 4 %Y A245991 Column 4 of A245995. %K A245991 nonn %O A245991 1,1 %A A245991 _R. H. Hardin_, Aug 09 2014