A074210 - OEIS

%I #12 Nov 18 2018 10:33:26

%S 1,4,12,30,272,4717,5402,18487,20115,28372,33998,111040,115170,456975,

%T 821586,1874660,4029676,4060029,59497900,232668002,313128068,529436220

%N 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.

%C No more terms through 20000000. - _Ryan Propper_, Jun 03 2006

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

%t 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 *)

%Y Cf. A000720, A074036.

%K more,nonn

%O 1,2

%A _Jason Earls_, Sep 19 2002

%E More terms from _Ryan Propper_, Jun 03 2006

%E a(19)-a(22) from _Donovan Johnson_, Oct 12 2008