A372670 - OEIS

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

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

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

LINKS

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

FORMULA

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

EXAMPLE

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

PROG