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A001360 Crystal ball sequence for hyperbolic tesselation 3^7 (from triangle group (2,3,7)). 0
1, 8, 29, 85, 232, 617, 1625, 4264, 11173, 29261, 76616, 200593, 525169, 1374920, 3599597, 9423877, 24672040, 64592249, 169104713, 442721896, 1159060981, 3034461053, 7944322184, 20798505505 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..23.

Index entries for crystal ball sequences

FORMULA

Conjecture: a(n) = 4*a(n-1)-4*a(n-2)+a(n-3). G.f.: (1+4*x+x^2)/((1-x)*(1-3*x+x^2)). [Colin Barker, Mar 16 2012]

CROSSREFS

Cf. A001354.

Sequence in context: A055536 A131438 A048478 * A116952 A199207 A088131

Adjacent sequences:  A001357 A001358 A001359 * A001361 A001362 A001363

KEYWORD

nonn,easy,nice

AUTHOR

N. J. A. Sloane.

STATUS

approved

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Last modified May 23 21:41 EDT 2013. Contains 225612 sequences.