OFFSET
0,2
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (3,-3,1).
FORMULA
From Amiram Eldar, Jan 25 2021: (Start)
Sum_{n>=1} 1/a(n) = Pi^2/294.
Sum_{n>=1} (-1)^(n+1)/a(n) = Pi^2/588.
Product_{n>=1} (1 + 1/a(n)) = sinh(Pi/7)/(Pi/7).
Product_{n>=1} (1 - 1/a(n)) = sin(Pi/7)/(Pi/7). (End)
From Elmo R. Oliveira, Nov 29 2024: (Start)
G.f.: 49*x*(1 + x)/(1-x)^3.
E.g.f.: 49*x*(1 + x)*exp(x).
a(n) = 3*a(n-1) - 3*a(n-2) + a(n-3) for n > 2. (End)
PROG
(Magma) [(7*n)^2: n in [0..50]]; // Vincenzo Librandi, May 21 2011
(PARI) a(n)=(7*n)^2 \\ Charles R Greathouse IV, Jun 17 2017
CROSSREFS
KEYWORD
nonn,easy,changed
AUTHOR
STATUS
approved