login
This site is supported by donations to The OEIS Foundation.

 

Logo

Thanks to everyone who made a donation during our annual appeal!
To see the list of donors, or make a donation, see the OEIS Foundation home page.

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A068489 m for which p(m) is the least prime dividing #p(n) - 1, i.e., one less than primorial n-th prime (A057588). 1
3, 10, 5, 343, 3248, 18, 16, 12, 22, 20324, 50, 9414916809095, 13120, 43, 8481, 1200361259, 196, 38, 10326732314, 65, 38, 34 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,1

COMMENTS

Since #P13 - 1 is a prime, see A006794, we need the number of primes less than or equal to #P13 - 1. The sequence continues 13120,43,8481,1200361259,196,38,10326732314,65,38,34,

a(24) = pi(23768741896345550770650537601358309). [Donovan Johnson, Dec 08 2009]

LINKS

Table of n, a(n) for n=2..23.

R. Mestrovic, Euclid's theorem on the infinitude of primes: a historical survey of its proofs (300 BC--2012) and another new proof, arXiv preprint arXiv:1202.3670, 2012 - From N. J. A. Sloane, Jun 13 2012

Hisanori Mishima, Factorization results #Pn (Primorial) - 1

FORMULA

PrimePi(A057713)

MATHEMATICA

Do[ Print[ PrimePi[ FactorInteger[ Product[ Prime[k], {k, 1, n}] - 1] [[1, 1]]]], {n, 2, 22} ]

CROSSREFS

Cf. A068488.

Sequence in context: A281220 A280529 A281279 * A088337 A195919 A275741

Adjacent sequences:  A068486 A068487 A068488 * A068490 A068491 A068492

KEYWORD

hard,more,nonn

AUTHOR

Lekraj Beedassy, Mar 11 2002

EXTENSIONS

Edited and extended by Robert G. Wilson v, Mar 12 2002

a(13) from Donovan Johnson, Dec 08 2009

STATUS

approved

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified January 15 23:42 EST 2019. Contains 319184 sequences. (Running on oeis4.)