A091629 Product of digits associated with A091628(n). Essentially the same as A007283.

6, 12, 24, 48, 96, 192, 384, 768, 1536, 3072, 6144, 12288, 24576, 49152, 98304, 196608, 393216, 786432, 1572864, 3145728, 6291456, 12582912, 25165824, 50331648, 100663296, 201326592, 402653184, 805306368, 1610612736, 3221225472

Offset

1,1

Comments

Sequence arising in Farideh Firoozbakht's solution to Prime Puzzle 251 - 23 is the only pointer prime (A089823) not containing digit "1".

The monotonic increasing value of successive product of digits strongly suggests that in successive n the digit 1 must be present.

Links

G. C. Greubel, Table of n, a(n) for n = 1..1000

Tanya Khovanova, Recursive Sequences

Carlos Rivera, Puzzle 251, Pointer primes, The Prime Puzzles and Problems Connection.

Index entries for linear recurrences with constant coefficients, signature (2).

Formula

a(n) = 3 * 2^n = product of digits of A091628(n).

From Philippe Deléham, Nov 23 2008: (Start)

a(n) = 6*2^(n-1).

a(n) = 2*a(n-1), with a(1) = 6.

G.f.: 6*x/(1-2*x). (End)

E.g.f.: 3*(exp(2*x) - 1). - G. C. Greubel, Jan 05 2023

Mathematica

3*2^Range[1, 60] (* Vladimir Joseph Stephan Orlovsky, Jun 09 2011 *)

Prog

(Magma) [3*2^n : n in [1..40]]; // Wesley Ivan Hurt, Jul 17 2020
(SageMath) [3*2^n for n in range(1, 51)] # G. C. Greubel, Jan 05 2023

Crossrefs

Sequences of the form (2*m+1)*2^n: A000079 (m=0), A007283 (m=1), A020714 (m=2), A005009 (m=3), A005010 (m=4), A005015 (m=5), A005029 (m=6), A110286 (m=7), A110287 (m=8), A110288 (m=9), A175805 (m=10), A248646 (m=11), A164161 (m=12), A175806 (m=13), A257548 (m=15).

Cf. A089823, A091628, A091630, A091631, A091632.

Similar to A003945, A042950, A058764, A087009.

Sequence in context: A362487 A229926 A082505 * A089529 A300915 A001766

Adjacent sequences: A091626 A091627 A091628 * A091630 A091631 A091632

Keyword

base,easy,nonn

Author

Enoch Haga, Jan 24 2004

Extensions

Edited and extended by Ray Chandler, Feb 07 2004

Status

approved