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A057809
Numbers n such that pi(n) divides n.
29
2, 4, 6, 8, 27, 30, 33, 96, 100, 120, 330, 335, 340, 350, 355, 360, 1008, 1080, 1092, 1116, 1122, 1128, 1134, 3059, 3066, 3073, 3080, 3087, 3094, 8408, 8424, 8440, 8456, 8464, 8472, 23526, 23535, 24300, 64540, 64580, 64610, 64620, 64650, 64690, 64700
OFFSET
1,1
COMMENTS
Each cluster of entries is approximately a power of e from the previous cluster.
LINKS
Giovanni Resta, Table of n, a(n) for n = 1..1161 (first 296 terms from Charles R Greathouse IV)
Konstantinos N. Gaitanas, An explicit formula for the prime counting function, arXiv preprint arXiv:1311.1398 [math.NT], 2013.
S. W. Golomb, On the Ratio of N to π(N), The American Mathematical Monthly 69.1 (1962): 36-37.
EXAMPLE
120 is a member as there are exactly 30 primes less than 120 and 30 * 4 = 120.
MAPLE
select(t -> t mod numtheory:-pi(t) = 0, [$2..10^5]); # Robert Israel, Jul 03 2016
MATHEMATICA
Select[ Range[2, 10^5], IntegerQ[ # / PrimePi[ # ]] & ]
Select[Range[1000], Divisible[#, PrimePi[#]] &] (* Requires version 6.0+. Alonso del Arte, May 24 2015 *)
PROG
(PARI) is(n)=n%primepi(n)==0 \\ Charles R Greathouse IV, Sep 14 2015
(Magma) [n: n in [2..10^5] | n mod #PrimesUpTo(n) eq 0]; // Vincenzo Librandi, Jul 04 2016
CROSSREFS
Apart from initial term same as A058011.
Sequence in context: A222712 A117912 A092047 * A135632 A068541 A329887
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Nov 07 2000
EXTENSIONS
More terms from James A. Sellers, Nov 08 2000
a(297)-a(1161) obtained from the values of A038625 computed by Jan Büthe. - Giovanni Resta, Aug 31 2018
STATUS
approved