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A027690 a(n) = n^2 + n + 5. 10
5, 7, 11, 17, 25, 35, 47, 61, 77, 95, 115, 137, 161, 187, 215, 245, 277, 311, 347, 385, 425, 467, 511, 557, 605, 655, 707, 761, 817, 875, 935, 997, 1061, 1127, 1195, 1265, 1337, 1411, 1487, 1565, 1645, 1727, 1811, 1897, 1985, 2075, 2167, 2261 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,1
LINKS
FORMULA
a(n) = A176271(n + 1, 3) for n > 1. - Reinhard Zumkeller, Apr 13 2010
a(n) = 2*n + a(n-1) for n>0, a(0)=5. - Vincenzo Librandi, Aug 05 2010
From Ilya Gutkovskiy, Nov 25 2016: (Start)
G.f.: (5 - 8*x + 5*x^2)/(1 - x)^3.
Sum_{n>=0} 1/a(n) = Pi*tanh(sqrt(19)*Pi/2)/sqrt(19) = 0.720729156259... (End)
MAPLE
with (combinat):seq(fibonacci(3, n)+n+4, n=0..47); # Zerinvary Lajos, Jun 07 2008
MATHEMATICA
Table[n^2 + n + 5, {n, 0, 100}] (* T. D. Noe, Oct 29 2009 *)
PROG
(PARI) a(n)=n^2+n+5 \\ Charles R Greathouse IV, Oct 07 2015
CROSSREFS
Sequence in context: A067830 A191019 A106862 * A087200 A153118 A060449
KEYWORD
nonn,easy
AUTHOR
EXTENSIONS
Corrected by T. D. Noe, Nov 09 2006
Definition and offset fixed by Franklin T. Adams-Watters, Jul 06 2009
STATUS
approved

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Last modified March 28 09:04 EDT 2024. Contains 371239 sequences. (Running on oeis4.)