login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A123341 a(1) = 1, a(n) = Sum_{k=1}^{Pi(n)} a(n-k) for n > 1, where Pi(n) is the number of primes less than or equal to n. 0
1, 1, 2, 3, 6, 11, 22, 42, 81, 156, 312, 613, 1226, 2430, 4818, 9555, 19110, 38064, 76128, 151944, 303275, 605324, 1210648, 2418866, 4832914, 9656273, 19293436, 38548808, 77097616, 154119104, 308238208, 616324472, 1232345669, 2464086014 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

Conjecture: lim_{n->infinity} a(n)/2^n > 0; appears to be about 0.1432645404.

LINKS

Table of n, a(n) for n=1..34.

FORMULA

a(1) = a(2) = 1, for p an odd prime, a(p) = 2a(p-1), otherwise a(n) = 2a(n-1) - a(n - pi(n) - 1).

CROSSREFS

Cf: A000720, A000045, A001590.

Sequence in context: A018613 A036589 A251656 * A238351 A043328 A141072

Adjacent sequences:  A123338 A123339 A123340 * A123342 A123343 A123344

KEYWORD

nonn

AUTHOR

Franklin T. Adams-Watters, Oct 11 2006

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified August 19 07:13 EDT 2022. Contains 356216 sequences. (Running on oeis4.)