A080258 Either 4th power of a prime, or product of a prime and the square of a different prime.

12, 16, 18, 20, 28, 44, 45, 50, 52, 63, 68, 75, 76, 81, 92, 98, 99, 116, 117, 124, 147, 148, 153, 164, 171, 172, 175, 188, 207, 212, 236, 242, 244, 245, 261, 268, 275, 279, 284, 292, 316, 325, 332, 333, 338, 356, 363, 369, 387, 388, 404, 412, 423, 425, 428, 436

Offset: 1

Author

Reinhard Zumkeller, Feb 10 2003

Keywords

• nonn

Comments

Union of A030514 and A054753.

Numbers that equal the product of the proper divisors of their proper divisors. - Scott R. Shannon, Jul 04 2021

Examples

			81=3*3*3*3 and 50=2*5*5 are terms.
		

Links

• Hugo Pfoertner, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A007964, A058080, A001221, A001222, A002033, A006881, A030078.

Programs

Mathematica

Module[{nn=20,p4,sdp},p4=Prime[Range[nn]]^4;sdp=#[[1]] #[[2]]^2&/@ Select[ Tuples[Prime[Range[nn]],2],#[[1]]!=#[[2]]&];Take[Join[p4,sdp]// Union,40]] (* Harvey P. Dale, Jan 31 2021 *)

PARI

is(n)=my(f=factor(n)[,2]~); f==[4] || f==[2,1] || f==[1,2] \\ Charles R Greathouse IV, Oct 16 2015

Formula

A080256(a(n)) = 5.

A002033(a(n)) = 8. - Juri-Stepan Gerasimov, Sep 26 2009