cp's OEIS Frontend

A026087 a(n) = number of (s(0), s(1), ..., s(n)) such that every s(i) is an integer, s(0) = 0, |s(i) - s(i-1)| = 1 for i = 1,2,3; |s(i) - s(i-1)| <= 1 for i >= 4, s(n) = 4. Also a(n) = T(n,n-4), where T is the array defined in A026082.

%I A026087 #6 Jun 23 2013 10:23:52
%S A026087 1,2,9,28,93,294,925,2872,8856,27136,82764,251472,761774,2301924,
%T A026087 6941898,20899680,62834397,188690634,566081421,1696873148,5082959517,
%U A026087 15216909686,45532045749,136182428520,407160436435,1216953379486,3636353333187
%N A026087 a(n) = number of (s(0), s(1), ..., s(n)) such that every s(i) is an integer, s(0) = 0, |s(i) - s(i-1)| = 1 for i = 1,2,3; |s(i) - s(i-1)| <= 1 for i >= 4, s(n) = 4. Also a(n) = T(n,n-4), where T is the array defined in A026082.
%F A026087 Conjecture: -(n-4)*(n+4)*a(n) +(4*n^2-11*n-27)*a(n-1) +(-2*n^2+29*n-24)*a(n-2) -(4*n+5)*(n-5)*a(n-3) +3*(n-5)*(n-6)*a(n-4)=0. - _R. J. Mathar_, Jun 23 2013
%Y A026087 First differences of A026071.
%K A026087 nonn
%O A026087 4,2
%A A026087 _Clark Kimberling_