OFFSET
0,1
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 0..2000
Eric Weisstein's MathWorld, Polygamma Function.
Wikipedia, Polygamma Function.
Index entries for linear recurrences with constant coefficients, signature (3,-3,1).
FORMULA
a(n) = a(n-1) + 50*n - 5; a(0)=4. - Vincenzo Librandi, Jun 07 2011
Sum_{n>=0} 1/a(n) = polygamma(1, 2/5)/25 = 0.2910142636... - Amiram Eldar, Oct 02 2020
a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3). - Wesley Ivan Hurt, Oct 02 2020
G.f.: -(4+x)*(1+9*x)/(-1+x)^3. - Wesley Ivan Hurt, Oct 02 2020
EXAMPLE
a(0) = (5*0 + 2)^2 = 4.
MATHEMATICA
(5*Range[0, 40]+2)^2 (* Harvey P. Dale, Feb 19 2011 *)
PROG
(Magma) [(5*n+2)^2: n in [0..40]]; // Vincenzo Librandi, Jun 07 2011
(PARI) a(n)=(5*n+2)^2 \\ Charles R Greathouse IV, Jun 17 2017
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
STATUS
approved