cp's OEIS Frontend

A256818 Number of length n+3 0..1 arrays with at most two downsteps in every n consecutive neighbor pairs.

%I A256818 #7 Jan 21 2018 09:37:29
%S A256818 16,32,64,128,245,442,753,1220,1894,2836,4118,5824,8051,10910,14527,
%T A256818 19044,24620,31432,39676,49568,61345,75266,91613,110692,132834,158396,
%U A256818 187762,221344,259583,302950,351947,407108,469000,538224,615416,701248
%N A256818 Number of length n+3 0..1 arrays with at most two downsteps in every n consecutive neighbor pairs.
%C A256818 Row 3 of A256816.
%H A256818 R. H. Hardin, <a href="/A256818/b256818.txt">Table of n, a(n) for n = 1..210</a>
%F A256818 Empirical: a(n) = (1/120)*n^5 + (1/12)*n^4 + (31/24)*n^3 - (31/12)*n^2 + (66/5)*n + 4.
%F A256818 Empirical g.f.: x*(16 - 64*x + 112*x^2 - 96*x^3 + 37*x^4 - 4*x^5) / (1 - x)^6. - _Colin Barker_, Jan 21 2018
%e A256818 Some solutions for n=4:
%e A256818 ..0....1....1....1....1....1....1....0....0....1....0....1....0....1....1....0
%e A256818 ..1....1....1....1....1....1....0....1....0....0....1....0....0....1....1....1
%e A256818 ..1....1....1....1....1....1....1....0....1....1....0....0....0....0....0....0
%e A256818 ..0....0....1....0....1....0....1....1....1....1....0....1....0....1....1....1
%e A256818 ..1....0....0....1....1....1....0....1....1....1....1....0....1....0....0....0
%e A256818 ..0....0....0....0....1....1....0....1....0....0....0....1....1....0....1....1
%e A256818 ..0....1....0....1....1....1....0....0....0....1....0....1....0....0....0....0
%Y A256818 Cf. A256816.
%K A256818 nonn
%O A256818 1,1
%A A256818 _R. H. Hardin_, Apr 10 2015