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 A255111 #10 Jan 25 2018 02:52:12 %S A255111 243,622,1137,1905,2951,4338,6141,8448,11361,14997,19489,24987,31659, %T A255111 39692,49293,60690,74133,89895,108273,129589,154191,182454,214781, %U A255111 251604,293385,340617,393825,453567,520435,595056,678093,770246,872253,984891 %N A255111 Number of length n+4 0..2 arrays with at most one downstep in every n consecutive neighbor pairs. %C A255111 Row 4 of A255107. %H A255111 R. H. Hardin, <a href="/A255111/b255111.txt">Table of n, a(n) for n = 1..210</a> %F A255111 Empirical: a(n) = (1/120)*n^5 + (7/24)*n^4 + (85/24)*n^3 + (1505/24)*n^2 + (2809/20)*n + 30 for n>2. %F A255111 Empirical g.f.: x*(243 - 836*x + 1050*x^2 - 447*x^3 - 219*x^4 + 339*x^5 - 156*x^6 + 27*x^7) / (1 - x)^6. - _Colin Barker_, Jan 24 2018 %e A255111 Some solutions for n=4: %e A255111 1 1 0 0 2 2 1 2 0 0 2 2 1 2 0 0 %e A255111 1 1 0 2 0 0 2 0 0 2 2 2 2 0 1 2 %e A255111 1 2 0 1 1 0 2 2 2 1 2 2 0 0 1 1 %e A255111 0 2 1 1 1 0 1 2 2 1 2 2 0 0 2 2 %e A255111 0 2 2 1 1 1 2 2 2 1 1 2 2 0 2 2 %e A255111 0 2 2 2 2 2 2 2 2 2 1 1 2 1 0 2 %e A255111 1 2 0 0 1 2 2 0 2 2 2 1 2 2 2 2 %e A255111 0 2 0 0 1 2 0 2 0 2 2 2 1 1 2 0 %Y A255111 Cf. A255107. %K A255111 nonn %O A255111 1,1 %A A255111 _R. H. Hardin_, Feb 14 2015