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A072326
Conjectured values of n such that the sum of proper divisors of x*n is never prime for any x >= 1 (i.e., sigma(xn) - xn is never prime for x >= 1).
1
42, 78, 84, 114, 126, 156, 168, 174, 186, 210
OFFSET
1,1
COMMENTS
From Michel Marcus, Jul 31 2017: (Start)
None of the given terms are correct.
For each term, here are some x such that sigma(n*x) - n*x is prime.
42, x: 5145000, 6923112, 7408800,
78, x: 26693550, 30371328,
114, x: 370386,
126, x: 1715000, 2307704, 2469600, 4390400, 5556600, 6860000,
156, x: 13346775, 15185664,
168, x: 1286250, 1730778, 1852200, 3292800, 4167450, 5145000,
174, x: 17400, 69600, 156600, 178176, 336864, 368184, 400896, 585336,
186, x: 2859936,
210, x: 1029000, 1481760, 2634240, 3333960, 4116000,
(End)
CROSSREFS
Sequence in context: A043769 A259737 A039525 * A068700 A303283 A135850
KEYWORD
dead
AUTHOR
Benoit Cloitre, Jul 31 2002
STATUS
approved