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A062404
Numbers k such that 2*k*prime(k) + 1 is prime.
1
1, 2, 3, 6, 7, 11, 16, 21, 24, 27, 29, 30, 33, 40, 43, 49, 50, 51, 54, 59, 60, 68, 76, 78, 90, 93, 95, 103, 120, 125, 131, 134, 139, 156, 159, 162, 168, 178, 180, 188, 189, 196, 198, 214, 225, 231, 237, 241, 243, 246, 255, 259, 268, 273, 275, 277, 280, 285, 287, 288
OFFSET
1,2
LINKS
EXAMPLE
2*3*prime(3) + 1 = 2 * 3 * 5 + 1 = 31 a prime.
MAPLE
select(i->isprime(2*i*ithprime(i)+1), [$1..300]); # Muniru A Asiru, Jun 29 2018
MATHEMATICA
Select[Range[300], PrimeQ[2# Prime[#]+1]&] (* Harvey P. Dale, Sep 12 2014 *)
PROG
(PARI) select(k->isprime(2*k*prime(k)+1), [1..700])
(Magma) [n: n in [1..300] |IsPrime(2*n*NthPrime(n) + 1)]; // Vincenzo Librandi, Jun 29 2018
CROSSREFS
Sequence in context: A096578 A027754 A092857 * A032875 A032842 A023773
KEYWORD
nonn
AUTHOR
Jason Earls, Jul 08 2001
STATUS
approved