A070226 Numbers n such that the squarefree kernel of n is equal to the number of divisors of n.

1, 2, 9, 12, 18, 80, 448, 625, 720, 1200, 1250, 1620, 2025, 4032, 4050, 5625, 7500, 9408, 11250, 11264, 20412, 35721, 53248, 71442, 101376, 117649, 235298, 280000, 371712, 479232, 768320, 907200, 1058841, 1114112, 1270080, 1411788, 1750000

Offset: 1

Author

Jason Earls, May 07 2002

Keywords

• nonn

Comments

Numbers n such that A007947(n)/A000005(n) = 1. [From Ctibor O. Zizka, Feb 05 2009]

Conjecture : If A000005(n) divides A007947(n) for some n, then A007947(n)=A000005(n). [From Ctibor O. Zizka, Feb 05 2009]

Links

• Donovan Johnson, Table of n, a(n) for n = 1..150

Crossrefs

Cf. A007947, A000005, A033950.

Programs

Mathematica

Select[Range[2000000],DivisorSigma[0,#]==Times@@Transpose[ FactorInteger[#]][[1]]&] (* Harvey P. Dale, Apr 09 2012 *)