A074210 Numbers k such that the number of primes <= k is equal to the sum of primes from the smallest prime factor of k to the largest prime factor of k.

1, 4, 12, 30, 272, 4717, 5402, 18487, 20115, 28372, 33998, 111040, 115170, 456975, 821586, 1874660, 4029676, 4060029, 59497900, 232668002, 313128068, 529436220

Offset

1,2

Comments

No more terms through 20000000. - Ryan Propper, Jun 03 2006

Links

Table of n, a(n) for n=1..22.

Example

pi(272) = 58 and 272 = 2^4*17 and 2+3+5+7+11+13+17 = 58, so 272 is a term.

Mathematica

Do[l = First /@ FactorInteger[n]; m = Range[First[l], Last[l]]; If[Plus @@ Select[m, PrimeQ] == PrimePi[n], Print[n]], {n, 2*10^7}] (* Ryan Propper, Jun 03 2006 *)

Crossrefs

Cf. A000720, A074036.

Sequence in context: A301875 A074252 A297079 * A299053 A005289 A037255

Adjacent sequences: A074207 A074208 A074209 * A074211 A074212 A074213

Keyword

more,nonn

Author

Jason Earls, Sep 19 2002

Extensions

More terms from Ryan Propper, Jun 03 2006

a(19)-a(22) from Donovan Johnson, Oct 12 2008

Status

approved