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 A027694 a(n) = n^2 + n + 9. 5
 9, 11, 15, 21, 29, 39, 51, 65, 81, 99, 119, 141, 165, 191, 219, 249, 281, 315, 351, 389, 429, 471, 515, 561, 609, 659, 711, 765, 821, 879, 939, 1001, 1065, 1131, 1199, 1269, 1341, 1415, 1491, 1569, 1649, 1731, 1815, 1901, 1989, 2079, 2171 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 LINKS Patrick De Geest, Palindromic Quasi_Over_Squares of the form n^2+(n+X). Index entries for linear recurrences with constant coefficients, signature (3,-3,1). FORMULA For n > 3, a(n) = A176271(n+1,5). - Reinhard Zumkeller, Apr 13 2010 G.f.: (-9 + 16*x - 9*x^2) / (x-1)^3. - R. J. Mathar, Feb 07 2011 a(0) = 9, a(n) = a(n - 1) + 2n. - Vincenzo Librandi, Feb 07 2011 Sum_{n>=0} 1/a(n) = Pi*tanh(Pi*sqrt(35)/2)/sqrt(35). - Amiram Eldar, Jan 17 2021 MAPLE with (combinat):seq(fibonacci(3, n)+n+8, n=0..46); # Zerinvary Lajos, Jun 07 2008 MATHEMATICA Table[n^2+n+9, {n, 0, 50}]  (* Harvey P. Dale, Feb 07 2011 *) PROG (PARI) a(n)=n^2+n+9 \\ Charles R Greathouse IV, Oct 07 2015 CROSSREFS Cf. A002522. Sequence in context: A287340 A037009 A163096 * A063191 A329167 A216976 Adjacent sequences:  A027691 A027692 A027693 * A027695 A027696 A027697 KEYWORD nonn,easy AUTHOR STATUS approved

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Last modified May 15 16:44 EDT 2021. Contains 343920 sequences. (Running on oeis4.)