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 A123720 a(n) = 2^n + 2^(n-1) - n. 9
 2, 4, 9, 20, 43, 90, 185, 376, 759, 1526, 3061, 6132, 12275, 24562, 49137, 98288, 196591, 393198, 786413, 1572844, 3145707, 6291434, 12582889, 25165800, 50331623, 100663270, 201326565, 402653156, 805306339, 1610612706, 3221225441 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Vincenzo Librandi, Table of n, a(n) for n = 1..1000 Index entries for linear recurrences with constant coefficients, signature (4,-5,2). FORMULA a(n) = A007283(n-1) - n. O.g.f.: x(2 - 4x + 3x^2)/((1-x)^2*(1-2x)). - R. J. Mathar, Jun 08 2008 E.g.f.: (1/2)*(-3 - 2*x*exp(x) + 3*exp(2*x)). - G. C. Greubel, Oct 26 2017 MATHEMATICA lst={}; Do[AppendTo[lst, 2^n+2^(n-1)-n], {n, 5!}]; lst (* and/or *) s=2; lst={s}; Do[s+=s+n++; AppendTo[lst, s], {n, 0, 5!}]; lst (* Vladimir Joseph Stephan Orlovsky, Oct 25 2008 *) Table[2^n + 2^{n-1) - n, {n, 1, 50}] (* or *) LinearRecurrence[{4, -5, 2}, {2, 4, 9}, 50] (* G. C. Greubel, Oct 26 2017 *) PROG (PARI) for(n=1, 31, print1(2^n+2^(n-1)-n, ", ")) (MAGMA) [2^n + 2^(n-1) - n: n in [1..40] ]; // Vincenzo Librandi, May 18 2011 CROSSREFS Cf. A007283. Sequence in context: A018102 A018103 A175104 * A179744 A266930 A034007 Adjacent sequences:  A123717 A123718 A123719 * A123721 A123722 A123723 KEYWORD nonn AUTHOR Klaus Brockhaus, Oct 09 2006 STATUS approved

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Last modified January 17 16:49 EST 2019. Contains 319235 sequences. (Running on oeis4.)