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A114569
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a(n) = 9*4^n - 1.
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4
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8, 35, 143, 575, 2303, 9215, 36863, 147455, 589823, 2359295, 9437183, 37748735, 150994943, 603979775, 2415919103, 9663676415, 38654705663, 154618822655, 618475290623, 2473901162495, 9895604649983, 39582418599935
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OFFSET
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0,1
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COMMENTS
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Squares of the cotangents of the arcsins of 1/(3*2^n).
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LINKS
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Vincenzo Librandi, Table of n, a(n) for n = 0..1000
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FORMULA
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From Philippe Deléham, Nov 26 2008: (Start)
a(n) = 4*a(n-1) + 3, n>0; a(0)=8.
a(n) = 5*a(n-1) - 4*a(n-2), n>1; a(0)=8, a(1)=35.
G.f.: (8-5*x)/(1-5*x+4*x^2). (End)
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EXAMPLE
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a(2) = 143.
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MATHEMATICA
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Table[(9*4^n) - 1, {n, 0, 23}] (* Stefan Steinerberger, Feb 16 2006 *)
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PROG
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(Magma) [9*4^n-1: n in [0..30]]; // Vincenzo Librandi, Oct 29 2011
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CROSSREFS
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Cf. A024036, A097743, A156760.
Sequence in context: A094616 A318020 A340522 * A189599 A302078 A320405
Adjacent sequences: A114566 A114567 A114568 * A114570 A114571 A114572
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KEYWORD
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easy,nonn
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AUTHOR
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Al Hakanson (hawkuu(AT)excite.com), Feb 16 2006
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EXTENSIONS
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More terms from Stefan Steinerberger, Feb 16 2006
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STATUS
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approved
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