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 A249285 #10 Nov 09 2018 21:54:53 %S A249285 204,660,2144,6960,22572,73204,237480,770416,2499164,8107012,26298608, %T A249285 85311248,276744204,897739412,2912207432,9447011744,30645489228, %U A249285 99411957620,322485877472,1046123080816,3393554802188,11008469603188 %N A249285 Number of length n+3 0..3 arrays with no four consecutive terms having the sum of any three elements equal to three times the fourth. %H A249285 R. H. Hardin, <a href="/A249285/b249285.txt">Table of n, a(n) for n = 1..210</a> %F A249285 Empirical: a(n) = 2*a(n-1) + 2*a(n-2) + 4*a(n-3) + 8*a(n-4) + 4*a(n-5) - 8*a(n-6) - 2*a(n-7) + 3*a(n-8). %F A249285 Empirical g.f.: 4*x*(51 + 63*x + 104*x^2 + 134*x^3 + 23*x^4 - 133*x^5 - 18*x^6 + 48*x^7) / (1 - 2*x - 2*x^2 - 4*x^3 - 8*x^4 - 4*x^5 + 8*x^6 + 2*x^7 - 3*x^8). - _Colin Barker_, Nov 09 2018 %e A249285 Some solutions for n=6: %e A249285 3 0 3 2 1 1 3 0 0 0 3 3 1 2 0 2 %e A249285 3 1 3 2 0 1 1 0 1 2 1 3 0 3 2 2 %e A249285 1 1 2 1 3 1 3 2 0 2 0 1 1 2 2 1 %e A249285 2 1 3 1 3 0 1 0 2 0 1 1 1 2 0 0 %e A249285 0 0 2 3 1 0 3 2 3 3 3 2 3 0 2 0 %e A249285 2 3 0 3 1 1 0 2 0 1 1 2 0 0 0 1 %e A249285 2 3 1 3 3 0 3 0 1 3 0 0 2 2 2 1 %e A249285 3 0 3 1 3 1 3 3 1 1 2 1 0 3 1 3 %e A249285 3 1 1 1 2 0 3 2 0 2 0 0 0 2 2 0 %Y A249285 Column 3 of A249290. %K A249285 nonn %O A249285 1,1 %A A249285 _R. H. Hardin_, Oct 24 2014