

A117587


Numbers k such that 2^prime(k)  prime(k)^2 is prime.


1



3, 4, 7, 8, 16, 23, 49, 89, 331, 497, 1122, 11222
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OFFSET

1,1


COMMENTS

No more terms below 5000.  Giovanni Resta, Apr 03 2006
p is a prime element of the sequence A072180 iff pi(p) is a term of A117587. So since 119087 is a prime term of A072180, pi(119087)= 11222 is in the sequence.  Farideh Firoozbakht, Dec 08 2006


LINKS

Table of n, a(n) for n=1..12.


EXAMPLE

4 is in the sequence because the 4th prime is 7 and 2^7  7^2 = 79 is a prime.


MAPLE

a:=proc(n) if isprime(2^ithprime(n)ithprime(n)^2) then n else fi end: seq(a(n), n=1..400); # Emeric Deutsch, Apr 06 2006


MATHEMATICA

Select[Range[1200], PrimeQ[2^#  #^2] &@ Prime@ # &] (* Michael De Vlieger, Feb 02 2019 *)


PROG

(PARI) for(i=1, 100, if(isprime(2^prime(i)prime(i)^2), print1(i, ", ")))


CROSSREFS

Cf. A072180.
Sequence in context: A050069 A219019 A306612 * A244930 A130420 A214096
Adjacent sequences: A117584 A117585 A117586 * A117588 A117589 A117590


KEYWORD

hard,more,nonn


AUTHOR

Mohammed Bouayoun (mohammed.bouayoun(AT)sanef.com), Apr 03 2006


EXTENSIONS

3 more terms from Giovanni Resta, Apr 03 2006
One more term from Farideh Firoozbakht, Dec 08 2006


STATUS

approved



