cp's OEIS Frontend

A256817 Number of length n+2 0..1 arrays with at most two downsteps in every n consecutive neighbor pairs.

%I A256817 #7 Jan 21 2018 09:37:21
%S A256817 8,16,32,64,124,229,402,673,1080,1670,2500,3638,5164,7171,9766,13071,
%T A256817 17224,22380,28712,36412,45692,56785,69946,85453,103608,124738,149196,
%U A256817 177362,209644,246479,288334,335707,389128,449160,516400,591480,675068
%N A256817 Number of length n+2 0..1 arrays with at most two downsteps in every n consecutive neighbor pairs.
%C A256817 Row 2 of A256816.
%H A256817 R. H. Hardin, <a href="/A256817/b256817.txt">Table of n, a(n) for n = 1..210</a>
%F A256817 Empirical: a(n) = (1/120)*n^5 + (1/24)*n^4 + (3/8)*n^3 - (1/24)*n^2 + (277/60)*n + 3.
%F A256817 Empirical g.f.: x*(8 - 32*x + 56*x^2 - 48*x^3 + 20*x^4 - 3*x^5) / (1 - x)^6. - _Colin Barker_, Jan 21 2018
%e A256817 Some solutions for n=4:
%e A256817 ..0....0....1....0....0....0....1....1....0....0....1....0....0....1....0....0
%e A256817 ..0....0....1....0....0....1....0....1....1....0....0....1....1....1....0....1
%e A256817 ..0....1....1....1....1....0....0....1....0....0....0....0....1....0....0....0
%e A256817 ..0....0....1....0....0....0....1....0....1....1....0....1....0....0....0....0
%e A256817 ..0....1....0....0....0....1....1....0....1....0....1....0....1....0....0....1
%e A256817 ..1....1....0....1....0....1....1....0....0....1....1....1....1....0....0....0
%Y A256817 Cf. A256816.
%K A256817 nonn
%O A256817 1,1
%A A256817 _R. H. Hardin_, Apr 10 2015