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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A063908 Numbers n such that n and 2n-3 are primes. 25
3, 5, 7, 11, 13, 17, 23, 31, 37, 41, 43, 53, 67, 71, 83, 97, 101, 107, 113, 127, 137, 157, 167, 181, 191, 193, 211, 223, 233, 241, 251, 263, 283, 311, 317, 331, 347, 373, 421, 431, 433, 443, 457, 461, 487, 521, 547, 563, 577, 587, 613, 617, 631 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

If p is in this sequence then the products of positive powers of 3, p and 2p-3 are entries in A086486. - Victoria A Sapko (vsapko(AT)canes.gsw.edu), Sep 23 2003

Median prime of AP3's starting at 3, i.e., triplets of primes (3,p,q) in arithmetic progression. - M. F. Hasler, Sep 24 2009

a(n) = sum of the coprimes(p) mod (p+1). - J. M. Bergot, Nov 13 2014

A010051(2*a(n)-3) = 1. - Reinhard Zumkeller, Jul 02 2015

LINKS

Harry J. Smith, Table of n, a(n) for n=1,...,1000

C. Rivera, Puzzle 34.- Prime Triplets in arithmetic progression. [From M. F. Hasler, Sep 24 2009]

FORMULA

A098090 INTERSECT A000040. - R. J. Mathar, Mar 23 2017

MATHEMATICA

Select[Prime[Range[6! ]], PrimeQ[2*#-3]&] (* Vladimir Joseph Stephan Orlovsky, Nov 17 2009 *)

PROG

(PARI) { n=0; p=1; for (m=1, 10^9, p=nextprime(p+1); if (isprime(2*p - 3), write("b063908.txt", n++, " ", p); if (n==1000, break)) ) } \\Harry J. Smith, Sep 02 2009

(PARI) forprime( p=1, default(primelimit), isprime(2*p-3) && print1(p", ")) \\ M. F. Hasler, Sep 24 2009

(MAGMA) [n : n in [0..700] | IsPrime(n) and IsPrime(2*n-3)]; // Vincenzo Librandi, Nov 14 2014

(Haskell)

a063908 n = a063908_list !! (n-1)

a063908_list = filter

   ((== 1) . a010051' . (subtract 3) . (* 2)) a000040_list

-- Reinhard Zumkeller, Jul 02 2015

CROSSREFS

Cf. A005382.

Cf. A000040, A010051, A088878, A172287.

Cf. A259730.

Sequence in context: A147545 A083668 A176116 * A154868 A274987 A020628

Adjacent sequences:  A063905 A063906 A063907 * A063909 A063910 A063911

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Aug 31 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 | More pages
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy .

Last modified June 25 06:13 EDT 2017. Contains 288709 sequences.