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A026015 a(n) = number of (s(0), s(1), ..., s(2n)) such that s(i) is a nonnegative integer and |s(i) - s(i-1)| = 1 for i = 1,2,...,n, s(0) = 2, s(2n) = 8. Also a(n) = T(2n,n-3), where T is the array defined in A026009. 1
1, 8, 45, 219, 987, 4248, 17748, 72675, 293436, 1172908, 4653935, 18366075, 72186075, 282861360, 1105877880, 4316224860, 16825024134, 65525448960, 255024693434, 992116674142, 3858537980286, 15004402265424, 58343871881400 (list; graph; refs; listen; history; text; internal format)
OFFSET

3,2

LINKS

Table of n, a(n) for n=3..25.

FORMULA

Conjecture: -(n+6)*(n-3)*a(n) +2*(3*n^2+3*n-20)*a(n-1) +(-9*n^2+15*n+20)*a(n-2) +2*(n-2)*(2*n-5)*a(n-3)=0. - R. J. Mathar, Jun 20 2013

CROSSREFS

First differences of A001392.

Sequence in context: A273267 A055222 A273305 * A002696 A016208 A216540

Adjacent sequences:  A026012 A026013 A026014 * A026016 A026017 A026018

KEYWORD

nonn

AUTHOR

Clark Kimberling

STATUS

approved

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Last modified October 15 14:07 EDT 2018. Contains 316236 sequences. (Running on oeis4.)