A026083 a(n) = number of (s(0), s(1), ..., s(n)) such that every s(i) is an integer, s(0) = 0 = s(n), |s(i) - s(i-1)| = 1 for i = 1,2,3; |s(i) - s(i-1)| <= 1 for i >= 4. Also a(n) = T(n,n), where T is the array defined in A026082.

6, 12, 38, 104, 300, 856, 2464, 7104, 20550, 59580, 173118, 503960, 1469546, 4291644, 12550290, 36746592, 107712306, 316050372, 928224594, 2728494360, 8026707864, 23630376000, 69614498268, 205212650272, 605292727450, 1786351811556

Offset

4,1

Comments

Third differences of the central trinomial numbers (A002426). - T. D. Noe, Mar 16 2005

Links

Table of n, a(n) for n=4..29.

Formula

Conjecture: n*a(n) +(-3*n+5)*a(n-1) +(-n-6)*a(n-2) +3*(n-5)*a(n-3)=0. - R. J. Mathar, Jun 22 2013

Crossrefs

Equals 2 * A024998(n-1). First differences of A024997.

Sequence in context: A117596 A276601 A096377 * A215179 A128453 A185616

Adjacent sequences: A026080 A026081 A026082 * A026084 A026085 A026086

Keyword

nonn

Author

Clark Kimberling

Status

approved