A026085 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) = 2. Also a(n) = T(n,n-2), where T is the array defined in A026082.

4, 8, 27, 76, 226, 660, 1939, 5688, 16704, 49072, 144254, 424296, 1248728, 3677184, 10834416, 31939584, 94205772, 277997400, 820747275, 2424232956, 7163519202, 21176638868, 62626464319, 185276853192, 548326714720, 1623325361424

Offset: 4

Author

Clark Kimberling

Keywords

• nonn

Crossrefs

First differences of A026069.

Formula

Conjecture: (n+2)*a(n) +(-5*n-1)*a(n-1) +4*(n-4)*a(n-2) +8*(n-1)*a(n-3) +(-5*n+34)*a(n-4) +3*(-n+7)*a(n-5)=0. - R. J. Mathar, Jun 23 2013