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

Author

Jason Earls, Sep 19 2002

Keywords

• more
• nonn

Comments

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

Examples

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

Crossrefs

Cf. A000720, A074036.

Programs

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 *)

Extensions

More terms from Ryan Propper, Jun 03 2006

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