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A094555
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Number of walks of length n between two vertices on the same triangular face of a truncated tetrahedron (triangular prism).
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5
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0, 1, 1, 6, 11, 46, 111, 386, 1051, 3366, 9671, 29866, 87891, 267086, 794431, 2396946, 7163531, 21545206, 64526391, 193797626, 580955971, 1743741726, 5229477551, 15691927906, 47068793211, 141220360646, 423633119911, 1270955283786
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,4
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COMMENTS
| Average of binomial and inverse binomial transforms of the Jacobsthal numbers A001045. - Paul Barry (pbarry(AT)wit.ie), Jan 04 2005
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FORMULA
| G.f. : x(1-x-x^2)/((1-x)(1+2x)(1-3x)); a(n)=3^n/6-(-2)^n/6+1/6-0^n/6; a(n)=2a(n-1)+5a(n-2)-6a(n-3).
a(n)=sum{k=0..floor(n/2), C(n, 2k)A001045(n-2k)} - Paul Barry (pbarry(AT)wit.ie), Jan 04 2005
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CROSSREFS
| Cf. A094554, A094556.
Sequence in context: A038265 A015440 A193488 * A099437 A077701 A177197
Adjacent sequences: A094552 A094553 A094554 * A094556 A094557 A094558
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KEYWORD
| easy,nonn
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AUTHOR
| Paul Barry (pbarry(AT)wit.ie), May 11 2004
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