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A026288 Number of (s(0), s(1), ..., s(n)) such that every s(i) is an integer, s(0) = 0, s(1) = 1, s(n) = 2, |s(i) - s(i-1)| <= 1 for i >= 2, |s(2) - s(1)| = 1, |s(3) - s(2)| = 1 if s(2) = 1. Also T(n,n-2), where T is the array in A026268. 0
1, 2, 5, 14, 38, 104, 285, 784, 2164, 5994, 16658, 46442, 129868, 364182, 1023960, 2886174, 8153952, 23086374, 65497653, 186175794, 530148414, 1512174076, 4320093569, 12360382436, 35414530188, 101603373430, 291864076387, 839402336610 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,2

LINKS

Table of n, a(n) for n=2..29.

FORMULA

G.f.: 8z^2(1-z)(1-z^2)/[1-z+sqrt(1-2z-3z^2)]^3.

Conjecture: (n+4)*a(n) +(-5*n-11)*a(n-1) +(5*n+2)*a(n-2) +(5*n-13)*a(n-3) +6*(-n+5)*a(n-4)=0. - R. J. Mathar, Jun 23 2013

CROSSREFS

Pairwise sums of A026123.

Sequence in context: A084085 A052985 A052945 * A047086 A006574 A053419

Adjacent sequences:  A026285 A026286 A026287 * A026289 A026290 A026291

KEYWORD

nonn

AUTHOR

Clark Kimberling

STATUS

approved

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Last modified October 23 06:58 EDT 2019. Contains 328335 sequences. (Running on oeis4.)