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A329855 Numbers k such that uphi(usigma(k)) = k where usigma is the sum of unitary divisors of k (A034448) and uphi is the unitary totient function (A047994). 1
1, 2, 3, 4, 6, 7, 8, 12, 14, 16, 24, 28, 31, 48, 56, 62, 112, 124, 127, 248, 254, 256, 496, 508, 768, 1016, 1792, 2032, 7936, 8191, 16382, 30240, 32512, 32764, 65528, 65536, 131056, 131071, 196608, 262142, 458752, 524284, 524287, 1048568, 1048574, 2031616 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..74 (terms below 5*10^10)

EXAMPLE

3 is in the sequence since uphi(usigma(3)) = uphi(4) = 3.

MATHEMATICA

usigma[1] = 1; usigma[n_] := Times @@ (1 + Power @@@ FactorInteger[n]); uphi[1] = 1; uphi[n_] := Times @@ (-1 + Power @@@ FactorInteger[n]); Select[Range[10^4], uphi[usigma[#]] == # &]

CROSSREFS

The unitary version of A001229.

Cf. A034448, A047994.

Sequence in context: A054784 A018585 A018399 * A029748 A018314 A212216

Adjacent sequences:  A329852 A329853 A329854 * A329856 A329857 A329858

KEYWORD

nonn

AUTHOR

Amiram Eldar, Nov 22 2019

STATUS

approved

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Last modified August 7 19:57 EDT 2020. Contains 336279 sequences. (Running on oeis4.)