A027691 a(n) = n^2 + n + 6.

6, 8, 12, 18, 26, 36, 48, 62, 78, 96, 116, 138, 162, 188, 216, 246, 278, 312, 348, 386, 426, 468, 512, 558, 606, 656, 708, 762, 818, 876, 936, 998, 1062, 1128, 1196, 1266, 1338, 1412, 1488, 1566, 1646, 1728, 1812, 1898, 1986, 2076, 2168, 2262

Offset

0,1

Links

Muniru A Asiru, Table of n, a(n) for n = 0..2000

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

a(n) = 2*n + a(n-1), with a(0)=6. - Vincenzo Librandi, Aug 05 2010

Sum_{n>=0} 1/a(n) = Pi*tanh(Pi*sqrt(23)/2)/sqrt(23). - Amiram Eldar, Jan 17 2021

Mathematica

Table[n^2+n+6, {n, 0, 100}] (* Vladimir Joseph Stephan Orlovsky, Mar 12 2011 *)

Prog

(PARI) a(n)=n^2+n+6 \\ Charles R Greathouse IV, Jun 17 2017
(GAP) List([0..50], n->n^2+n+6); # Muniru A Asiru, Jul 15 2018

Crossrefs

Cf. A002061, A002378, A002522.

Sequence in context: A315864 A315865 A315866 * A146529 A062533 A315867

Adjacent sequences: A027688 A027689 A027690 * A027692 A027693 A027694

Keyword

nonn,easy

Author

Patrick De Geest

Extensions

Offset changed by Charles R Greathouse IV, Jul 25 2010

Status

approved