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A329856
Numbers k such that usigma(uphi(k)) = k where usigma is the sum of unitary divisors of k (A034448) and uphi is the unitary totient function (A047994).
1
1, 3, 4, 5, 8, 9, 12, 17, 20, 24, 32, 36, 40, 68, 72, 96, 128, 136, 160, 257, 288, 384, 544, 640, 1028, 1152, 2056, 2176, 8192, 8224, 24576, 32896, 40960, 44352, 65537, 73728, 131072, 139264, 262148, 393216, 524288, 524296, 655360, 1179648, 1572864, 2097184
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 usigma(uphi(3)) = usigma(2) = 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], usigma[uphi[#]] == # &]
CROSSREFS
The unitary version of A018784.
Sequence in context: A256173 A050070 A050590 * A327984 A066906 A125884
KEYWORD
nonn
AUTHOR
Amiram Eldar, Nov 22 2019
STATUS
approved