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 A229013 #17 Sep 13 2018 11:00:25 %S A229013 2,15,46,101,186,307,470,681,946,1271,1662,2125,2666,3291,4006,4817, %T A229013 5730,6751,7886,9141,10522,12035,13686,15481,17426,19527,21790,24221, %U A229013 26826,29611,32582,35745,39106,42671,46446,50437,54650,59091,63766,68681,73842 %N A229013 Number of arrays of median of three adjacent elements of some length-5 0..n array, with no adjacent equal elements in the latter. %H A229013 R. H. Hardin, <a href="/A229013/b229013.txt">Table of n, a(n) for n = 1..210</a> %F A229013 Empirical: a(n) = n^3 + 3*n^2 - 3*n + 1. %F A229013 Conjectures from _Colin Barker_, Sep 13 2018: (Start) %F A229013 G.f.: x*(2 - x)*(1 + 4*x + x^2) / (1 - x)^4. %F A229013 a(n) = 4*a(n-1) - 6*a(n-2) + 4*a(n-3) - a(n-4) for n>4. %F A229013 (End) %e A229013 Some solutions for n=4: %e A229013 ..2....1....1....3....3....0....4....2....1....2....2....0....2....2....0....1 %e A229013 ..1....4....0....0....4....1....2....1....2....1....4....2....2....0....3....3 %e A229013 ..3....1....3....3....1....1....2....4....0....2....3....3....3....2....2....3 %Y A229013 Row 3 of A229012. %K A229013 nonn %O A229013 1,1 %A A229013 _R. H. Hardin_, Sep 10 2013