A026084 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) = 1. Also a(n) = T(n,n-1), where T is the array defined in A026082.

3, 13, 33, 98, 278, 804, 2320, 6723, 19515, 56769, 165421, 482793, 1411049, 4129323, 12098151, 35482857, 104169033, 306087111, 900134883, 2649106752, 7801834068, 22992061134, 67799076002, 200040038589, 590529542053, 1744148984223

Offset: 4

Author

Clark Kimberling

Keywords

• nonn

Crossrefs

First differences of A024998.

Formula

Conjecture: (n+1)*a(n) +3*(-n+1)*a(n-1) +(-n-9)*a(n-2) +3*(n-5)*a(n-3)=0. - R. J. Mathar, Jun 23 2013