OFFSET
0,1
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 0..10000
Index entries for linear recurrences with constant coefficients, signature (4,-6,4,-1).
FORMULA
G.f.: 27*(1 + 60*x + 93*x^2 + 8*x^3)/ (x-1)^4. - R. J. Mathar, Aug 01 2014
a(n) = 27*A016779(n). - R. J. Mathar, Aug 01 2014
From Amiram Eldar, Oct 03 2024: (Start)
a(n) = A017197(n)^3.
Sum_{n>=0} 1/a(n) = 2*Pi^3/(2187*sqrt(3)) + 13*zeta(3)/729. (End)
MATHEMATICA
(9Range[0, 30]+3)^3 (* or *) LinearRecurrence[{4, -6, 4, -1}, {27, 1728, 9261, 27000}, 30] (* Harvey P. Dale, Jun 20 2024 *)
PROG
(Magma) [(9*n+3)^3: n in [0..30]]; // Vincenzo Librandi, Jul 23 2011
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
STATUS
approved