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A122973
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Number of vertices on the surface of an icosahedron.
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0
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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; internal format)
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OFFSET
| 0,2
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LINKS
| Index to sequences with linear recurrences with constant coefficients, signature (5,-4).
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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)=5a(n-1)-4a(n-2) [From Harvey P. Dale, May 05 2011]
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MATHEMATICA
| Join[{1}, LinearRecurrence[{5, -4}, {12, 42}, 30]] (* or *) CoefficientList[ Series[1-6x (-2+3x)/((4x-1)(x-1)), {x, 0, 30}], x] (* From Harvey P. Dale, May 05 2011 *)
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CROSSREFS
| Cf. A005901.
Sequence in context: A009948 A193068 A007586 * A074356 A172294 A088826
Adjacent sequences: A122970 A122971 A122972 * A122974 A122975 A122976
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KEYWORD
| nonn,easy
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AUTHOR
| Alden Chew (aldenc98(AT)yahoo.com), Oct 27 2006
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