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A089531 Primes p such that (p-3)/2 is also prime. 13
7, 13, 17, 29, 37, 41, 61, 89, 97, 109, 137, 149, 181, 197, 229, 257, 277, 281, 317, 337, 349, 389, 397, 401, 449, 457, 461, 541, 557, 569, 617, 677, 701, 709, 761, 769, 797, 821, 881, 929, 937, 977, 1009, 1021, 1049, 1097, 1117, 1129, 1201, 1217, 1229, 1237 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

FORMULA

a(n) = 2*A023204(n) + 3.

MATHEMATICA

Clear[lst, n, f] f[n_]:=PrimeQ[(n-3)/2]; lst={}; Do[p=Prime[n]; If[f[p], AppendTo[lst, p]], {n, 6!}]; lst (* Vladimir Joseph Stephan Orlovsky, Oct 13 2009 *)

Select[Prime[Range[300]], PrimeQ[(# - 3) / 2]&] (* Vincenzo Librandi, Apr 13 2013 *)

PROG

(MAGMA) [p: p in PrimesUpTo(1300) | IsPrime((p-3) div 2)]; // Vincenzo Librandi, Apr 13 2013

(PARI) is(n)=isprime(n) && isprime((n-3)\2) \\ Charles R Greathouse IV, Sep 09 2014

CROSSREFS

Cf. A023204, A089530, A089532.

Sequence in context: A167276 A181570 A154408 * A247010 A138337 A174877

Adjacent sequences:  A089528 A089529 A089530 * A089532 A089533 A089534

KEYWORD

nonn,easy

AUTHOR

Ray Chandler, Nov 07 2003

EXTENSIONS

Comment from Juri-Stepan Gerasimov used as new name (old name moved to formulas). - Charles R Greathouse IV, Sep 09 2014

STATUS

approved

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Last modified August 24 18:12 EDT 2019. Contains 326295 sequences. (Running on oeis4.)