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A084295 n is such that pi(n*prime(n))/n is an integer. 2
1, 3, 47, 88, 200, 547, 12182, 15335, 39104, 58122, 73282, 150740 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

a(9) > 30000. - Michel Marcus, Sep 02 2019

a(13) > 200000. - Giovanni Resta, Sep 02 2019

LINKS

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

MATHEMATICA

Do[s=PrimePi[n*Prime[n]]/n; If[IntegerQ[s], Print[n]], {n, 1, 100000}]

Select[Range[16000], IntegerQ[PrimePi[#*Prime[#]]/#]&] (* Harvey P. Dale, Jul 23 2015 *)

PROG

(PARI) isok(n) = denominator(primepi(n*prime(n))/n) == 1; \\ Michel Marcus, Sep 02 2019

CROSSREFS

Cf. A000040, A000720, A033286, A057855, A084297, A084298.

Sequence in context: A227171 A055058 A139845 * A141850 A003551 A054643

Adjacent sequences:  A084292 A084293 A084294 * A084296 A084297 A084298

KEYWORD

nonn,hard,more

AUTHOR

Labos Elemer, May 27 2003

EXTENSIONS

Corrected by Harvey P. Dale, Jul 23 2015

a(9)-a(12) from Giovanni Resta, Sep 02 2019

STATUS

approved

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Last modified October 23 03:21 EDT 2019. Contains 328335 sequences. (Running on oeis4.)