A288834 a(n) = (n+1) * 3^(n-1).

2, 9, 36, 135, 486, 1701, 5832, 19683, 65610, 216513, 708588, 2302911, 7440174, 23914845, 76527504, 243931419, 774840978, 2453663097, 7748409780, 24407490807, 76709256822, 240588123669, 753145430616, 2353579470675, 7343167948506, 22876792454961

Offset

1,1

Links

Table of n, a(n) for n=1..26.

Index entries for linear recurrences with constant coefficients, signature (6,-9).

Formula

O.g.f.: z*(2-3*z)/(1-3*z)^2.

a(n) = -A287768(n+1,2).

a(n) = (n+1)*A000244(n-1). - Felix Fröhlich, Jun 19 2017

a(n) = A027471(n)/3 for n >= 3. - Art Baker, Apr 12 2019

From Amiram Eldar, Jan 18 2021: (Start)

Sum_{n>=1} 1/a(n) = 9*log(3/2) - 3.

Sum_{n>=1} (-1)^(n+1)/a(n) = 3 - 9*log(4/3). (End)

Mathematica

Table[(n + 1)*3^(n - 1), {n, 27}] (* Michael De Vlieger, Jun 23 2017 *)
LinearRecurrence[{6, -9}, {2, 9}, 40] (* Harvey P. Dale, Dec 16 2018 *)

Prog

(PARI) a(n) = (n+1)*3^(n-1) \\ Felix Fröhlich, Jun 19 2017
(PARI) Vec((z*(2-3*z)/(1-3*z)^2) + O(z^30)) \\ Felix Fröhlich, Jun 19 2017

Crossrefs

Cf. A000244, A027471, A287768.

Sequence in context: A192694 A192702 A073989 * A134759 A007946 A135593

Adjacent sequences: A288831 A288832 A288833 * A288835 A288836 A288837

Keyword

nonn

Author

Gregory Gerard Wojnar, Jun 17 2017

Status

approved