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A026290 a(n) = number of (s(0), s(1), ..., s(n)) such that every s(i) is an integer, s(0) = 0, s(1) = 1, s(n) = 4, |s(i) - s(i-1)| <= 1 for i >=2, |s(2) - s(1)| = 1, |s(3) - s(2)| = 1 if s(2) = 1. Also a(n) = T(n,n-4), where T is the array in A026268. 0
1, 4, 14, 46, 145, 446, 1349, 4034, 11966, 35290, 103642, 303458, 886548, 2585922, 7534245, 21934524, 63826041, 185668816, 540034074, 1570719570, 4568920029, 13292253106, 38679350746, 112583530784, 327793747775, 954702193796 (list; graph; refs; listen; history; text; internal format)
OFFSET

4,2

LINKS

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

FORMULA

G.f.: 32z^4(1-z)(1-z^2)/[1-z+sqrt(1-2z-3z^2)]^5.

CROSSREFS

Pairwise sums of A026145.

Pairwise sums of A026125.

Sequence in context: A054449 A029868 A030267 * A027649 A049221 A081670

Adjacent sequences:  A026287 A026288 A026289 * A026291 A026292 A026293

KEYWORD

nonn

AUTHOR

Clark Kimberling

STATUS

approved

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Last modified January 23 03:08 EST 2019. Contains 319370 sequences. (Running on oeis4.)