%I A026030
%S A026030 1,4,15,56,209,780,2912,10880,40698,152456,572033,2150040,8095425,30535260,
%T A026030 115377660,436698240,1655607390,6286707000,23908446510,91057063344,
%U A026030 347281885818,1326262602104,5071418015120,19415851639296,74419447792340
%N A026030 a(n) = number of (s(0), s(1), ..., s(2n)) such that s(i) is a nonnegative 
               integer and |s(i) - s(i-1)| = 1 for i = 1,2,...,n, s(0) = 3, s(2n) 
               = 5. Also a(n) = T(2n,n-1), where T is defined in A026022.
%F A026030 C(2n, n-1) - C(2n, n-5). G.f.: (1+x^2C^4)*C^4, where C=(1-sqrt(1-4x))/
               (2x). - Ralf Stephan, Jan 09 2005
%Y A026030 Sequence in context: A001353 A106707 A125905 this_sequence A047038 A158500 
               A001791
%Y A026030 Adjacent sequences: A026027 A026028 A026029 this_sequence A026031 A026032 
               A026033
%K A026030 nonn
%O A026030 2,2
%A A026030 Clark Kimberling (ck6(AT)evansville.edu)