cp's OEIS Frontend

A026018 a(n) = number of (s(0), s(1), ..., s(2n-1)) such that s(i) is a nonnegative integer and |s(i) - s(i-1)| = 1 for i = 1,2,...,n, s(0) = 2, s(2n-1) = 7. Also a(n) = T(2n-1,n-3), where T is the array defined in A026009.

%I A026018 #6 Jun 20 2013 16:26:58
%S A026018 1,7,36,164,702,2898,11696,46512,183141,716243,2788060,10817820,
%T A026018 41880930,161900910,625272480,2413491360,9313307370,35936613414,
%U A026018 138680365704,535290282632,2066802226236,7983111461732,30848211650592
%N A026018 a(n) = number of (s(0), s(1), ..., s(2n-1)) such that s(i) is a nonnegative integer and |s(i) - s(i-1)| = 1 for i = 1,2,...,n, s(0) = 2, s(2n-1) = 7. Also a(n) = T(2n-1,n-3), where T is the array defined in A026009.
%F A026018 Conjecture: -(n+5)*(3*n-37)*a(n) +3*(-n^2-84*n-173)*a(n-1) +2*(32*n^2+295*n+254)*a(n-2) -8*(n+25)*(2*n-5)*a(n-3)=0. - _R. J. Mathar_, Jun 20 2013
%Y A026018 First differences if A003518.
%K A026018 nonn
%O A026018 3,2
%A A026018 _Clark Kimberling_