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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

%I

%S 42,78,84,114,126,156,168,174,186,210

%N 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).

%C From _Michel Marcus_, Jul 31 2017: (Start)

%C None of the given terms are correct.

%C For each term, here are some x such that sigma(n*x) - n*x is prime.

%C 42, x: 5145000, 6923112, 7408800,

%C 78, x: 26693550, 30371328,

%C 114, x: 370386,

%C 126, x: 1715000, 2307704, 2469600, 4390400, 5556600, 6860000,

%C 156, x: 13346775, 15185664,

%C 168, x: 1286250, 1730778, 1852200, 3292800, 4167450, 5145000,

%C 174, x: 17400, 69600, 156600, 178176, 336864, 368184, 400896, 585336,

%C 186, x: 2859936,

%C 210, x: 1029000, 1481760, 2634240, 3333960, 4116000,

%C (End)

%K dead

%O 1,1

%A _Benoit Cloitre_, Jul 31 2002

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Last modified May 10 05:05 EDT 2021. Contains 343748 sequences. (Running on oeis4.)