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A023208 Numbers n such that n and 3n + 2 both prime. 38
3, 5, 7, 13, 17, 19, 23, 29, 37, 43, 59, 79, 83, 89, 97, 103, 127, 139, 149, 163, 167, 173, 197, 199, 227, 233, 239, 257, 269, 293, 313, 317, 337, 349, 353, 367, 383, 397, 409, 419, 433, 439, 457, 479, 499, 503, 523, 569, 577, 607, 643, 659, 709, 757, 769, 797, 859, 863 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Also, son primes of order 1. For smallest son primes of order n see A136027 (also definition). For son primes of order 2 see A136082 - Artur Jasinski, Dec 12 2007

LINKS

Zak Seidov and Michael De Vlieger, Table of n, a(n) for n = 1..10000 (first 1000 terms from Zak Seidov)

Rosemary Sullivan and Neil Watling, Independent divisibility pairs on the set of integers from 1 to n, INTEGERS 13 (2013) #A65.

MATHEMATICA

n = 1; a = {}; Do[If[PrimeQ[(Prime[k] - 2n)/(2n + 1)], AppendTo[a, (Prime[k] - 2n)/(2n + 1)]], {k, 1, 1000}]; a (* Artur Jasinski, Dec 12 2007 *)

PROG

(PARI) isA023208(n) = isprime(n) && isprime(3*n+2) \\ Michael B. Porter, Jan 30 2010

(MAGMA) [n: n in PrimesUpTo(900) | IsPrime(3*n+2)]; // Vincenzo Librandi, Nov 20 2010

(Haskell)

a023208 n = a023208_list !! (n-1)

a023208_list = filter ((== 1) . a010051 . (+ 2) . (* 3)) a000040_list

-- Reinhard Zumkeller, Aug 15 2011

CROSSREFS

Cf. A023208, A094524, A136019, A136020, A136026, A136027, A136082, A136083, A136084, A136085, A136086, A136087, A136088, A136089, A136090, A136091.

Sequence in context: A031163 A106119 A152820 * A162358 A154320 A173912

Adjacent sequences:  A023205 A023206 A023207 * A023209 A023210 A023211

KEYWORD

nonn,easy

AUTHOR

David W. Wilson

EXTENSIONS

Edited by N. J. A. Sloane, May 16 2008 at the suggestion of R. J. Mathar

STATUS

approved

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Last modified November 15 06:23 EST 2019. Contains 329144 sequences. (Running on oeis4.)