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A176509 Composite numbers m for which A064380(m)=A000010(m). 9
8, 27, 125, 128, 343, 1331, 2187, 2197, 4913, 6859, 12167, 24389, 29791, 32768, 50653, 68921, 78125, 79507, 103823, 148877, 205379, 226981, 300763, 357911, 389017, 493039, 571787, 704969, 823543, 912673, 1030301, 1092727 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Theorem. A064380(m)=A000010(m) iff m has the form m=p^(2^k-1), k>=1, p a prime. Eliminating the primes (k=1), the terms of the sequence have this form for k>1. All terms of A030078 (k=2) and A092759 (k=3) and prime powers of A010803 (k=4) are in the sequence, for example.

LINKS

Table of n, a(n) for n=1..32.

FORMULA

a(n) ~ n^3 log^3 n. - Charles R Greathouse IV, Feb 19 2013

PROG

(PARI) is(n)=my(e=isprimepower(n)); e>2 && 2^valuation(e+1, 2)==e+1 \\ Charles R Greathouse IV, Feb 19 2013

CROSSREFS

Cf. A000010, A064380, A176472, A050376, A030078, A056824.

Sequence in context: A331285 A183316 A045971 * A179125 A030160 A030162

Adjacent sequences:  A176506 A176507 A176508 * A176510 A176511 A176512

KEYWORD

nonn

AUTHOR

Vladimir Shevelev, Apr 19 2010

EXTENSIONS

128 inserted, 1024 deleted, 2187 inserted, 32768 inserted etc [R. J. Mathar, Nov 21 2010

STATUS

approved

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Last modified January 27 14:29 EST 2021. Contains 340467 sequences. (Running on oeis4.)