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A372670
Numbers k such that k * phi(k) is a fifth power.
1
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
1,2
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
(PARI) isok(n) = ispower(n*eulerphi(n), 5);
CROSSREFS
KEYWORD
nonn
AUTHOR
Seiichi Manyama, May 10 2024
STATUS
approved