OFFSET
1,1
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..10000
Index entries for linear recurrences with constant coefficients, signature (3,-3,1).
FORMULA
From Vincenzo Librandi, Feb 08 2012: (Start)
900*a(n) + 1 = (450*n + 1)^2.
G.f.: 2*x*(113 + 112*x)/(1-x)^3.
a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3). (End)
E.g.f.: x*(226 + 225*x)*exp(x). - G. C. Greubel, Jun 10 2021
MATHEMATICA
LinearRecurrence[{3, -3, 1}, {226, 902, 2028}, 50] (* Vincenzo Librandi, Feb 08 2012 *)
PROG
(PARI) a(n)=225*n^2+n \\ Charles R Greathouse IV, Dec 23 2011
(Magma) I:=[226, 902, 2028]; [n le 3 select I[n] else 3*Self(n-1)-3*Self(n-2)+1*Self(n-3): n in [1..50]]; // Vincenzo Librandi, Feb 08 2012
(Sage) [n*(1+225*n) for n in [1..50]] # G. C. Greubel, Jun 10 2021
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Vincenzo Librandi, Feb 16 2009
STATUS
approved