A104904 Numbers n such that d(n)*pi(n)=n, where d(n) is the number of positive divisors of n.

2, 8408, 481044, 189961452, 75370122528, 75370124832, 4086199302976, 221945984411264

Offset

1,1

Comments

Next term is greater than 3*10^9.

Links

Table of n, a(n) for n=1..8.

Example

189961452 is in the sequence because d(189961452)=18; pi(189961452)=10553414 & 18*10553414=189961452.

Mathematica

Do[If[DivisorSigma[0, n]*PrimePi[n] == n, Print[n]], {n, 2000000000}]

Crossrefs

Cf. A063903, A104905, A104906.

Sequence in context: A322126 A272241 A171939 * A272247 A167748 A203755

Adjacent sequences: A104901 A104902 A104903 * A104905 A104906 A104907

Keyword

hard,more,nonn

Author

Farideh Firoozbakht, Apr 12 2005

Extensions

a(5)-a(8) from Donovan Johnson, Dec 08 2009

Status

approved