OFFSET
0,3
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (6,-12,8).
FORMULA
G.f.: 8*x^2/(1 - 2*x)^3. - Vincenzo Librandi, Feb 10 2013
a(n) = 8*A001788(n-1). - R. J. Mathar, Apr 26 2015
From Amiram Eldar, Jul 11 2020: (Start)
Sum_{n>=2} 1/a(n) = (1 - log(2))/2.
Sum_{n>=2} (-1)^n/a(n) = (3*log(3/2) - 1)/2. (End)
E.g.f.: 4*exp(2*x)*x^2. - Stefano Spezia, Sep 02 2024
MATHEMATICA
CoefficientList[Series[8 x^2/(1 - 2 x)^3, {x, 0, 30}], x] (* Vincenzo Librandi, Feb 10 2013 *)
PROG
(Magma) [(n^2-n)*2^n: n in [0..30]]; // Vincenzo Librandi, Feb 10 2013
(PARI) a(n)=n*(n-1)<<n \\ Charles R Greathouse IV, Sep 24 2015
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Mohammad K. Azarian, Apr 07 2007
STATUS
approved