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

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Last modified March 30 10:34 EDT 2023. Contains 361609 sequences. (Running on oeis4.)