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A030518 Number of walks of length n between two vertices on a icosahedron at distance 2. 3
0, 2, 8, 52, 248, 1302, 6448, 32552, 162448, 813802, 4067448, 20345052, 101717448, 508626302, 2543092448, 12715657552, 63578092448 (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). - Emeric Deutsch (deutsch(AT)duke.poly.edu), Apr 03 2004

CROSSREFS

Sequence in context: A191480 A013555 A018987 * A123188 A027329 A136794

Adjacent sequences:  A030515 A030516 A030517 * A030519 A030520 A030521

KEYWORD

nonn

AUTHOR

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

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Last modified February 16 15:27 EST 2012. Contains 205930 sequences.