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
KEYWORD
nonn,easy
AUTHOR
STATUS
approved