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 A036800 a(n) = -6 + 2^(n+1)*(3 - 2*n + n^2). 7
 0, 2, 18, 90, 346, 1146, 3450, 9722, 26106, 67578, 169978, 417786, 1007610, 2392058, 5603322, 12976122, 29753338, 67633146, 152567802, 341835770, 761266170, 1686110202, 3716153338, 8153726970, 17817403386, 38788923386 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS This sequence is a part of a class of sequences of the type: a(n) = sum(i=0,n,(C^i)*(i^k)). This sequence has C=2, k=2. Sequence A036799 has C=2, k=1. Suppose C>=2, k>=1 are integers. What is the general closed form for a(n)? - Ctibor O. Zizka, Feb 07 2008 REFERENCES M. Petkovsek et al., A=B, Peters, 1996, p. 97. Jolley, Summation of Series, Dover (1961), p. 6. LINKS Vincenzo Librandi, Table of n, a(n) for n = 0..1000 S. Sykora, Finite and Infinite Sums of the Power Series (k^p)(x^k), DOI 10.3247/SL1Math06.002, Section V. Index entries for linear recurrences with constant coefficients, signature (7,-18,20,-8). FORMULA a(n) = Sum_{k=0..n} 2^k * k^2. - Benoit Cloitre, Jun 11 2003 From R. J. Mathar, Oct 03 2011: (Start) G.f.: 2*x*(1+2*x) / ( (x-1)*(2*x-1)^3 ). a(n) = 2*A036826(n). (End) a(0)=0, a(1)=2, a(2)=18, a(3)=90, a(n)=7*a(n-1)-18*a(n-2)+ 20*a(n-3)- 8*a(n-4). - Harvey P. Dale, Jun 13 2015 a(n) = Sum_{k=0..n} Sum_{i=0..n} k^2 * C(k,i). - Wesley Ivan Hurt, Sep 21 2017 MATHEMATICA Table[ -6+2^(n+1)*(3-2*n+n^2), {n, 0, 5!}] (* Vladimir Joseph Stephan Orlovsky, Mar 08 2010 *) LinearRecurrence[{7, -18, 20, -8}, {0, 2, 18, 90}, 30] (* Harvey P. Dale, Jun 13 2015 *) PROG (MAGMA) [-6+2^(n+1)*(3-2*n+n^2): n in [0..30]]; // Vincenzo Librandi, Oct 04 2011 (PARI) a(n)=2^(n+1)*(3 - 2*n + n^2) - 6 \\ Charles R Greathouse IV, Jun 11 2015 CROSSREFS Cf. A232599, A232600, A232601, A232602. Sequence in context: A172529 A201236 A206623 * A157052 A280157 A224616 Adjacent sequences:  A036797 A036798 A036799 * A036801 A036802 A036803 KEYWORD nonn,easy AUTHOR STATUS approved

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Last modified November 20 06:06 EST 2018. Contains 317385 sequences. (Running on oeis4.)