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A087865 Numbers m such that the number of primes less than 3^m is itself prime. 1
2, 53, 16097, 120739, 334349, 18703411700669 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

The sequence lists the prime terms of A055729.

That is, sequence is also: numbers m such that primepi(3^m) is prime.

LINKS

Table of n, a(n) for n=1..6.

MATHEMATICA

Select[ Table[ PrimePi[ 3^n], {n, 0, 49}], PrimeQ@# &] (* Robert G. Wilson v, Feb 25 2010 *)

PROG

(PARI) primeslessxn2(n, p) = /*primes < p^n if prime */ { sr=0; for(x=0, n, y=primepi(p^x); if(y<>0, sr+=1.0/y); if(isprime(y), print1(y", ")); ); print(); print(sr) }

CROSSREFS

Cf. A055729 (number of primes <= 3^n).

Sequence in context: A176946 A265443 A234603 * A278843 A083471 A078691

Adjacent sequences:  A087862 A087863 A087864 * A087866 A087867 A087868

KEYWORD

nonn,more

AUTHOR

Cino Hilliard, Oct 27 2003

EXTENSIONS

a(6) added by David Baugh, Mar 17 2015

STATUS

approved

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Last modified March 28 05:38 EDT 2020. Contains 333073 sequences. (Running on oeis4.)