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A114887 Multiperfect numbers sigma(n) = k*n, which are divisible by the sum of their prime factors without repetition. 4
120, 672, 32760, 2178540, 1379454720, 14182439040, 518666803200, 30823866178560, 71065075104190073088, 154345556085770649600, 9186050031556349952000, 680489641226538823680000 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
From a list of about 5000 multiperfect numbers, 38 numbers were found with the property, all having k <= 9, the largest was the only one having k=9. A091443 uses sopfr with repetition.
Conjecture: the sequence is finite.
LINKS
Sven Simon, Table of n, a(n) for n = 1..38 [Conjectured to be complete]
Achim Flammenkamp, The Multiply Perfect Numbers Page (See here for the latest information about the search)
Eric Weisstein's World of Mathematics, Multiperfect numbers
EXAMPLE
a(0) = 120 = 2^3*3*5, sopf(120) = 2+3+5 = 10.
CROSSREFS
Cf. A091443.
Intersection of A007691 and A089352. - Michel Marcus, Oct 08 2017
Sequence in context: A113546 A281771 A166069 * A069085 A039688 A005820
KEYWORD
nonn
AUTHOR
Sven Simon, Feb 19 2006
STATUS
approved

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Last modified July 18 07:53 EDT 2024. Contains 374377 sequences. (Running on oeis4.)