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A122973 Number of vertices on the surface of an icosahedron. 1
1, 12, 42, 162, 642, 2562, 10242, 40962, 163842, 655362, 2621442, 10485762, 41943042, 167772162, 671088642, 2684354562, 10737418242, 42949672962, 171798691842, 687194767362, 2748779069442, 10995116277762, 43980465111042, 175921860444162, 703687441776642 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..24.

Index entries for linear recurrences with constant coefficients, signature (5,-4).

FORMULA

a(n) = 1 if n=0, 10*4^(n-1)+2 otherwise.

G.f.: 1-6*x*(-2+3*x) / ( (4*x-1)*(x-1) ). - R. J. Mathar, Feb 02 2011

For a(n)>1: a(1)=12, a(2)=42, a(n) = 5*a(n-1)-4*a(n-2). [Harvey P. Dale, May 05 2011]

MATHEMATICA

Join[{1}, LinearRecurrence[{5, -4}, {12, 42}, 30]] (* or *) CoefficientList[ Series[1-6x (-2+3x)/((4x-1)(x-1)), {x, 0, 30}], x] (* Harvey P. Dale, May 05 2011 *)

CROSSREFS

Cf. A005901.

Sequence in context: A193068 A007586 A228391 * A074356 A172294 A238225

Adjacent sequences:  A122970 A122971 A122972 * A122974 A122975 A122976

KEYWORD

nonn,easy

AUTHOR

Alden Chew (aldenc98(AT)yahoo.com), Oct 27 2006

STATUS

approved

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Last modified October 22 20:57 EDT 2018. Contains 316502 sequences. (Running on oeis4.)