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 A255988 #8 Jan 24 2018 14:03:07 %S A255988 26,45,80,144,256,451,796,1413,2510,4448,7872,13943,24718,43817,77636, %T A255988 137540,243712,431899,765360,1356169,2403034,4258172,7545592,13370799, %U A255988 23692770,41983189,74394040,131826104,233594880,413927683,733476228 %N A255988 Number of length n+4 0..1 arrays with at most one downstep in every 4 consecutive neighbor pairs. %C A255988 Column 4 of A255992. %H A255988 R. H. Hardin, <a href="/A255988/b255988.txt">Table of n, a(n) for n = 1..210</a> %F A255988 Empirical: a(n) = 2*a(n-1) -a(n-2) +3*a(n-4) -2*a(n-5). %F A255988 Empirical g.f.: x*(26 - 7*x + 16*x^2 + 29*x^3 - 30*x^4) / (1 - 2*x + x^2 - 3*x^4 + 2*x^5). - _Colin Barker_, Jan 24 2018 %e A255988 Some solutions for n=4: %e A255988 ..1....1....0....1....0....0....1....1....1....1....0....0....0....1....1....1 %e A255988 ..1....0....0....1....0....1....0....0....1....1....0....1....1....1....0....1 %e A255988 ..1....0....0....0....1....1....0....0....1....1....0....0....0....1....0....0 %e A255988 ..0....1....0....1....1....0....0....0....1....1....1....1....0....0....0....0 %e A255988 ..1....1....1....1....0....0....0....1....1....0....1....1....0....0....1....1 %e A255988 ..1....0....1....1....0....0....0....0....1....1....1....1....1....0....0....1 %e A255988 ..1....0....1....1....0....1....1....0....0....1....1....0....1....1....0....1 %e A255988 ..1....1....0....1....1....0....0....0....1....1....0....0....0....0....1....0 %Y A255988 Cf. A255992. %K A255988 nonn %O A255988 1,1 %A A255988 _R. H. Hardin_, Mar 13 2015