OFFSET
0,1
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 0..10000
Index entries for linear recurrences with constant coefficients, signature (3,-3,1).
FORMULA
a(n) = A017221(n)^2.
a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3). - Harvey P. Dale, May 22 2012
G.f.: (25 + 121*x + 16*x^2)/(1-x)^3. - R. J. Mathar, Mar 20 2018
From G. C. Greubel, Dec 29 2022: (Start)
a(2*n+1) = 4*A017246(n).
a(n) = a(n-1) + 9*(18*n + 1).
E.g.f.: (25 + 171*x + 81*x^2)*exp(x). (End)
MATHEMATICA
(9Range[0, 30]+5)^2 (* or *) LinearRecurrence[{3, -3, 1}, {25, 196, 529}, 30] (* Harvey P. Dale, May 22 2012 *)
PROG
(Magma) [(9*n+5)^2: n in [0..35]]; // Vincenzo Librandi, Jul 24 2011
(PARI) a(n)=(9*n+5)^2 \\ Charles R Greathouse IV, Jun 17 2017
(SageMath) [(9*n+5)^2 for n in range(41)] # G. C. Greubel, Dec 29 2022
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
STATUS
approved