login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A059788 Largest prime < 2*prime(n). 7
3, 5, 7, 13, 19, 23, 31, 37, 43, 53, 61, 73, 79, 83, 89, 103, 113, 113, 131, 139, 139, 157, 163, 173, 193, 199, 199, 211, 211, 223, 251, 257, 271, 277, 293, 293, 313, 317, 331, 337, 353, 359, 379, 383, 389, 397, 421, 443, 449, 457, 463, 467, 479, 499, 509, 523 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Also, smallest member of the first pair of consecutive primes such that between them is a composite number divisible by the n-th prime. - Amarnath Murthy, Sep 25 2002

Except for its initial term, A006992 is a subsequence based on iteration of n -> A151799(2n). The range of this sequence is a subset of A065091. - M. F. Hasler, May 08 2016

LINKS

Zak Seidov, Table of n, a(n) for n = 1..1000

FORMULA

a(n) = A007917(A100484(n)). - R. J. Mathar, May 08 2016

EXAMPLE

n=18: p(18)=61, so the largest prime before 122 is a(18)=113.

MAPLE

with(numtheory):

A059788 := proc(n)

    prevprime(2*ithprime(n)) ;

end proc:

seq(A059788(n), n=1..50) ; # R. J. Mathar, May 08 2016

MATHEMATICA

a[n_] := Prime[PrimePi[2Prime[n]]]

NextPrime[2*Prime[Range[100]], -1] (* Zak Seidov, May 08 2016 *)

PROG

(PARI) a(n) = precprime(2*prime(n)); \\ Michel Marcus, May 08 2016

CROSSREFS

Cf. A005382, A005383, A005384, A005385, A055496, A006992, A052248.

Sequence in context: A127459 A174635 A075579 * A077171 A171602 A155189

Adjacent sequences:  A059785 A059786 A059787 * A059789 A059790 A059791

KEYWORD

nonn

AUTHOR

Labos Elemer, Feb 22 2001

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 July 8 19:20 EDT 2020. Contains 335524 sequences. (Running on oeis4.)