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 A065532 a(n) = 48*n^2 - 1. 2
 -1, 47, 191, 431, 767, 1199, 1727, 2351, 3071, 3887, 4799, 5807, 6911, 8111, 9407, 10799, 12287, 13871, 15551, 17327, 19199, 21167, 23231, 25391, 27647, 29999, 32447, 34991, 37631, 40367, 43199, 46127, 49151, 52271, 55487, 58799, 62207, 65711, 69311, 73007, 76799 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS Harry J. Smith, Table of n, a(n) for n = 0..1000 Index entries for linear recurrences with constant coefficients, signature (3,-3,1). FORMULA From Vincenzo Librandi, Jul 08 2012: (Start) G.f.: (1 - 50*x - 47*x^2)/(x-1)^3. a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3). (End) From Amiram Eldar, Mar 19 2023: (Start) Sum_{n>=1} 1/a(n) = (1 - cot(Pi/(4*sqrt(3)))*Pi/(4*sqrt(3)))/2. Sum_{n>=1} (-1)^(n+1)/a(n) = (cosec(Pi/(4*sqrt(3)))*Pi/(4*sqrt(3)) - 1)/2. (End) MATHEMATICA CoefficientList[Series[(1-50*x-47*x^2)/(x-1)^3, {x, 0, 40}], x] (* Vincenzo Librandi, Jul 08 2012 *) LinearRecurrence[{3, -3, 1}, {-1, 47, 191}, 40] (* Harvey P. Dale, Dec 13 2017 *) PROG (PARI) A065532(n)=48*n^2-1 (PARI) { for (n=0, 1000, write("b065532.txt", n, " ", 48*n^2 - 1) ) } \\ Harry J. Smith, Oct 21 2009 (Magma) [48*n^2 - 1: n in [0..50]]; // Vincenzo Librandi, Jul 08 2012 CROSSREFS Sequence in context: A204610 A158632 A142413 * A157362 A141874 A224325 Adjacent sequences: A065529 A065530 A065531 * A065533 A065534 A065535 KEYWORD sign,easy AUTHOR Labos Elemer, Nov 28 2001 EXTENSIONS Better description from Randall L Rathbun, Jan 19 2002 Offset changed from 1 to 0 by Harry J. Smith, Oct 21 2009 STATUS approved

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Last modified March 3 20:15 EST 2024. Contains 370512 sequences. (Running on oeis4.)