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A285615 Numbers n such that usigma(n) >= 3n, where usigma(n) = sum of unitary divisors of n (A034448). 5
30030, 39270, 43890, 46410, 51870, 53130, 62790, 66990, 67830, 71610, 79170, 82110, 84630, 85470, 91770, 94710, 99330, 101010, 103530, 108570, 111930, 117390, 122430, 128310, 136290, 140910, 144690, 154770, 161070, 164010, 166530, 168630, 182490, 191730 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Unitary 3-abundant numbers, correspond to 3-abundant numbers (A023197).

Similarly, the first numbers n such that usigma(n) >= 4n are 200560490130, 7420738134810, 8222980095330, and 8624101075590. - Giovanni Resta, Apr 23 2017

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..100

MATHEMATICA

usigma[n_] := If[n == 1, 1, Times @@ (1 + Power @@@ FactorInteger[n])]; Select[Range[100000], usigma[#] >= 3*# &]

CROSSREFS

Cf. A034448, A023197, A034683.

Sequence in context: A074969 A066765 A067885 * A336671 A258361 A072940

Adjacent sequences:  A285612 A285613 A285614 * A285616 A285617 A285618

KEYWORD

nonn

AUTHOR

Amiram Eldar, Apr 22 2017

STATUS

approved

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Last modified October 27 05:51 EDT 2020. Contains 338035 sequences. (Running on oeis4.)