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 A024038 a(n) = 4^n - n^2. 2
 1, 3, 12, 55, 240, 999, 4060, 16335, 65472, 262063, 1048476, 4194183, 16777072, 67108695, 268435260, 1073741599, 4294967040, 17179868895, 68719476412, 274877906583, 1099511627376, 4398046510663, 17592186043932 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS Vincenzo Librandi, Table of n, a(n) for n = 0..500 Guo-Niu Han, Enumeration of Standard Puzzles Guo-Niu Han, Enumeration of Standard Puzzles [Cached copy] Index entries for linear recurrences with constant coefficients, signature (7,-15,13,-4). FORMULA a(n) = A000325(n)*A006127(n). - Reinhard Zumkeller, Apr 10 2010 G.f.: (1-4*x+6*x^2+3*x^3)/((1-x)^3*(1-4*x)). - Colin Barker, May 29 2012 MATHEMATICA Table[4^n-n^2, {n, 0, 30}] (* or *) LinearRecurrence[{7, -15, 13, -4}, {1, 3, 12, 55}, 30] (* Harvey P. Dale, Sep 14 2013 *) PROG (MAGMA) [ 4^n-n^2: n in [0..30] ]; // Vincenzo Librandi, Dec 25 2010 CROSSREFS Cf. A000302, A000290. - Reinhard Zumkeller, Apr 10 2010 Sequence in context: A180589 A042971 A256142 * A007199 A179848 A001764 Adjacent sequences:  A024035 A024036 A024037 * A024039 A024040 A024041 KEYWORD nonn,easy AUTHOR STATUS approved

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Last modified December 9 16:41 EST 2018. Contains 318023 sequences. (Running on oeis4.)