A026069 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; |s(i) - s(i-1)| <= 1 for i >= 3, s(n) = 2. Also a(n) = T(n,n-2), where T is the array defined in A024996.

1, 5, 13, 40, 116, 342, 1002, 2941, 8629, 25333, 74405, 218659, 642955, 1891683, 5568867, 16403283, 48342867, 142548639, 420546039, 1241293314, 3665526270, 10829045472, 32005684340, 94632148659, 279909001851, 828235716571, 2451561077995

Offset: 3

Author

Clark Kimberling

Keywords

• nonn

Crossrefs

First differences of A025180. Second differences of A014531.

Extensions

a(29) corrected by Sean A. Irvine, Sep 14 2019