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A054027
Numbers that do not divide their sum of divisors.
2
2, 3, 4, 5, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74
OFFSET
1,1
MAPLE
with(numtheory): [seq(`if`(sigma(i) mod i <> 0, i, print( )), i=1..90)];
MATHEMATICA
Select[Range[100], !Divisible[DivisorSigma[1, #], #]&] (* Harvey P. Dale, May 29 2019 *)
PROG
(PARI) isok(m) = (sigma(m) % m) != 0; \\ Michel Marcus, Jun 20 2021
CROSSREFS
Complement of A007691. Cf. A000203, A054024.
Sequence in context: A097010 A351227 A132999 * A272978 A080907 A127161
KEYWORD
nonn
AUTHOR
Asher Auel, Jan 19 2000
STATUS
approved