A054888 - OEIS

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A054888

Layer counting sequence for hyperbolic tessellation by regular pentagons of angle Pi/2.

1, 5, 15, 40, 105, 275, 720, 1885, 4935, 12920, 33825, 88555, 231840, 606965, 1589055, 4160200, 10891545, 28514435, 74651760, 195440845, 511670775, 1339571480, 3507043665, 9181559515, 24037634880, 62931345125 (list; graph; refs; listen; history; internal format)

	OFFSET	`1,2`
	COMMENTS	`The layer sequence is the sequence of the cardinalities of the layers accumulating around a (finite-sided) polygon of the tessellation under successive side-reflections.`
	LINKS	`Illustration` `Reinhard Zumkeller, Table of n, a(n) for n = 1..1000`
	FORMULA	`G.f.: (1+x)^2/(x^2-3x+1).` `a(n) = A0001906(n-1)+2A001906(n)+A001906(n+1). - R. J. Mathar, Nov 28 2011` `a(n) = A203976(A004277(n-1)). [Reinhard Zumkeller, Jan 11 2012]`
	PROG	`(Haskell)` `a054888 n = a054888_list !! (n-1)` `a054888_list = 1 : zipWith (+) (tail a002878_list) a002878_list` `-- Reinhard Zumkeller, Jan 11 2012`
	CROSSREFS	`{a(n)/5} for n>1 is A001906.` `Cf. A002878.` `Sequence in context: A152881 A000333 A201157 * A038066 A113861 A080870` `Adjacent sequences: A054885 A054886 A054887 * A054889 A054890 A054891`
	KEYWORD	`nonn`
	AUTHOR	`Paolo Dominici (pl.dm(AT)libero.it), May 23 2000`

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Last modified February 15 14:20 EST 2012. Contains 205811 sequences.