A372670 Numbers k such that k * phi(k) is a fifth power.

1, 8, 256, 500, 864, 8192, 9826, 16000, 27648, 54000, 132651, 209952, 246924, 262144, 314432, 333396, 512000, 884736, 1061208, 1562500, 1728000, 6718464, 7002306, 7294032, 7901568, 8388608, 8541936, 10061824, 10668672, 13122000, 13564278, 15432750, 16384000

Offset: 1

Author

Seiichi Manyama, May 10 2024

Keywords

• nonn

Comments

To look for terms it suffices to see if fifth powers have a divisors pair (k, m) such that phi(m) = k. - David A. Corneth, May 21 2024

Examples

			8 * phi(8) = 32 = 2^5.
		

Links

• David A. Corneth, Table of n, a(n) for n = 1..8846 (first 38 terms from R. J. Mathar)

Crossrefs

Cf. A000584, A002618, A114076.

Programs

PARI

isok(n) = ispower(n*eulerphi(n), 5);

Formula

If n is in the sequence and prime p divides n, then p^5*n is in the sequence.