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A026071 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) = 4. Also a(n) = T(n,n-4), where T is the array defined in A024996. 2
1, 3, 12, 40, 133, 427, 1352, 4224, 13080, 40216, 122980, 374452, 1136226, 3438150, 10380048, 31279728, 94114125, 282804759, 848886180, 2545759328, 7628718845, 22845628531, 68377674280, 204560102800, 611720539235, 1828673918721 (list; graph; refs; listen; history; text; internal format)
OFFSET

4,2

COMMENTS

First differences of A025182.

LINKS

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

FORMULA

Conjecture: -(n-4)*(n+4)*a(n) +(4*n+7)*(n-4)*a(n-1) +(-2*n^2+23*n-12)*a(n-2) -(4*n+3)*(n-4)*a(n-3) +3*(n-4)*(n-5)*a(n-4)=0. - R. J. Mathar, Jun 22 2013

CROSSREFS

Sequence in context: A027991 A120304 A289652 * A102839 A050182 A222610

Adjacent sequences:  A026068 A026069 A026070 * A026072 A026073 A026074

KEYWORD

nonn

AUTHOR

Clark Kimberling

STATUS

approved

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Last modified February 23 00:33 EST 2018. Contains 299473 sequences. (Running on oeis4.)