A013730 a(n) = 2^(3n+1).

2, 16, 128, 1024, 8192, 65536, 524288, 4194304, 33554432, 268435456, 2147483648, 17179869184, 137438953472, 1099511627776, 8796093022208, 70368744177664, 562949953421312, 4503599627370496, 36028797018963968, 288230376151711744, 2305843009213693952

Offset

0,1

Comments

1/2 + 1/16 + 1/128 + 1/1024 + ... = 4/7. - Gary W. Adamson, Aug 29 2008

Links

Vincenzo Librandi, Table of n, a(n) for n = 0..200

Tanya Khovanova, Recursive Sequences.

Index entries for linear recurrences with constant coefficients, signature (8).

Index to divisibility sequences.

Formula

From Philippe Deléham, Nov 23 2008: (Start)

a(n) = 8*a(n-1), n > 0; a(0)=2.

G.f.: 2/(1-8x). (End)

a(n) = A157176(A016921(n)) = A157176(A016933(n)). - Reinhard Zumkeller, Feb 24 2009

From Amiram Eldar, May 08 2023: (Start)

Sum_{n>=0} (-1)^n/a(n) = 4/9.

Product_{n>=0} (1 - 1/a(n)) = A132024. (End)

Maple

seq(2^(3*n+1), n=0..19); # Nathaniel Johnston, Jun 26 2011

Mathematica

Table[2^n, {n, 1, 100, 3}] (* and *) 2^(3*Range[0, 40] + 1) (* Vladimir Joseph Stephan Orlovsky, Jun 14 2011 *)

Prog

(Magma) [2^(3*n+1): n in [0..30]]; // Vincenzo Librandi, May 04 2011
(PARI) a(n)=2<<(3*n) \\ Charles R Greathouse IV, Jun 14 2011

Crossrefs

Cf. A013731, A016921, A016933, A132024, A157176.

Sequence in context: A022027 A322297 A338933 * A270924 A371814 A214623

Adjacent sequences: A013727 A013728 A013729 * A013731 A013732 A013733

Keyword

nonn,easy

Author

N. J. A. Sloane

Status

approved