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A023208
Primes p such that 3*p + 2 is also prime.
42
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
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
KEYWORD
nonn,easy
EXTENSIONS
Edited by N. J. A. Sloane, May 16 2008 at the suggestion of R. J. Mathar
STATUS
approved