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 A090288 a(n) = 2*n^2 + 6*n + 2. 19
 2, 10, 22, 38, 58, 82, 110, 142, 178, 218, 262, 310, 362, 418, 478, 542, 610, 682, 758, 838, 922, 1010, 1102, 1198, 1298, 1402, 1510, 1622, 1738, 1858, 1982, 2110, 2242, 2378, 2518, 2662, 2810, 2962, 3118, 3278, 3442, 3610, 3782, 3958, 4138, 4322, 4510 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 COMMENTS Values of polynomial K_2 related to A090285: a(n) = K_2(n) = Sum_{k>=0} A090285(2,k)*2^k*binomial(n,k). Numbers n such that 2*n+5 is a square. - Vincenzo Librandi, Oct 10 2013 a(n) is the area of a triangle with vertices at (b(n-2),b(n-1)), (b(n),b(n+1)), and (b(n+2),B(n+3)) for b(k)=A000292(k) with n>1. - J. M. Bergot, Mar 23 2017 LINKS Vincenzo Librandi, Table of n, a(n) for n = 0..1000 Index entries for linear recurrences with constant coefficients, signature (3,-3,1). FORMULA a(n) = 2*A028387(n). G.f.: 2*(-1-2*x+x^2)/(-1+x)^3. - R. J. Mathar, Apr 02 2008 a(n) = 4*(n+1)+a(n-1), with n>0, a(0)=2. - Vincenzo Librandi, Nov 16 2010 E.g.f.: 2(x^2 + 4*x + 1)*exp(x). - G. C. Greubel, Jul 13 2017 MATHEMATICA Array[ -#*(2-#*2)-2&, 5!, 2] (* Vladimir Joseph Stephan Orlovsky, Dec 21 2008 *) Table[(2 n^2 + 6 n + 2), {n, 0, 80}] (* Vincenzo Librandi, Oct 10 2013 *) LinearRecurrence[{3, -3, 1}, {2, 10, 22}, 50] (* Harvey P. Dale, May 04 2017 *) PROG (PARI) a(n)=2*n^2+6*n+2 \\ Charles R Greathouse IV, Sep 24 2015 CROSSREFS Cf. A028387, A090285. Sequence in context: A273993 A225290 A065450 * A032526 A294538 A096183 Adjacent sequences:  A090285 A090286 A090287 * A090289 A090290 A090291 KEYWORD nonn,easy AUTHOR Philippe Deléham, Jan 25 2004 EXTENSIONS Corrected by T. D. Noe, Nov 12 2006 STATUS approved

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