login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
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. 0
1, 4, 12, 30, 272, 4717, 5402, 18487, 20115, 28372, 33998, 111040, 115170, 456975, 821586, 1874660, 4029676, 4060029, 59497900, 232668002, 313128068, 529436220 (list; graph; refs; listen; history; text; internal format)
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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified July 13 15:18 EDT 2020. Contains 335688 sequences. (Running on oeis4.)