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 A255110 #10 Jan 25 2018 02:52:08 %S A255110 81,216,441,789,1302,2032,3042,4407,6215,8568,11583,15393,20148,26016, %T A255110 33184,41859,52269,64664,79317,96525,116610,139920,166830,197743, %U A255110 233091,273336,318971,370521,428544,493632,566412,647547,737737,837720,948273 %N A255110 Number of length n+3 0..2 arrays with at most one downstep in every n consecutive neighbor pairs. %C A255110 Row 3 of A255107. %H A255110 R. H. Hardin, <a href="/A255110/b255110.txt">Table of n, a(n) for n = 1..210</a> %F A255110 Empirical: a(n) = (1/120)*n^5 + (1/4)*n^4 + (59/24)*n^3 + (93/4)*n^2 + (1321/30)*n + 11. %F A255110 Empirical g.f.: x*(81 - 270*x + 360*x^2 - 237*x^3 + 78*x^4 - 11*x^5) / (1 - x)^6. - _Colin Barker_, Jan 24 2018 %e A255110 Some solutions for n=4: %e A255110 1 0 2 0 2 0 2 0 2 0 2 0 1 0 0 0 %e A255110 0 2 1 1 0 0 2 2 0 0 0 2 1 0 1 0 %e A255110 0 0 1 1 0 0 2 1 0 0 0 1 2 0 0 0 %e A255110 0 0 1 1 1 0 2 2 1 0 1 1 0 0 0 1 %e A255110 1 1 1 2 1 0 0 2 1 0 1 2 2 1 0 2 %e A255110 1 2 0 0 2 1 0 2 1 0 0 2 2 2 0 2 %e A255110 1 1 2 1 2 2 2 1 2 0 2 1 2 2 0 0 %Y A255110 Cf. A255107. %K A255110 nonn %O A255110 1,1 %A A255110 _R. H. Hardin_, Feb 14 2015