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
From Elmo R. Oliveira, Oct 28 2024: (Start)
G.f.: 2*(3 - 5*x + 3*x^2)/(1 - x)^3.
E.g.f.: (2*(3 + x) + x^2)*exp(x).
a(n) = 2*A152950(n+1). (End)
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
KEYWORD
nonn,easy
AUTHOR
EXTENSIONS
Offset changed by Charles R Greathouse IV, Jul 25 2010
STATUS
approved