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A030517 Number of walks of length n between two vertices on a icosahedron at distance 1. 3
1, 2, 13, 52, 273, 1302, 6573, 32552, 163073, 813802, 4070573, 20345052, 101733073, 508626302, 2543170573, 12715657552, 63578483073 (list; graph; refs; listen; history; internal format)
OFFSET

1,2

FORMULA

A030517(n)=2*A030517(n-1)+2*A030518(n-1)+5*A030517(n-2), A030518(n)=2*A030517(n-1)+2*A030518(n-1)+5*A030518(n-2)

a(n)=5^n/12-(-1)^n/12+(sqrt(5))^(n+1)/20+(-sqrt(5))^(n+1)/20. a(n)=4a(n-1)+10a(n-2)-20a(n-3)-25a(n-4) for n>=5. - Emeric Deutsch (deutsch(AT)duke.poly.edu), Apr 03 2004

CROSSREFS

Sequence in context: A056297 A037383 A034476 * A048502 A177077 A144235

Adjacent sequences:  A030514 A030515 A030516 * A030518 A030519 A030520

KEYWORD

nonn

AUTHOR

Yasutoshi Kohmoto (zbi74583(AT)boat.zero.ad.jp)

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Last modified February 17 02:48 EST 2012. Contains 205978 sequences.