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A205524 Numbers n such that gcd(n, sigma(n)) is not equal to sigma(n) mod n. 3
4, 8, 9, 10, 14, 15, 16, 21, 22, 25, 26, 27, 30, 32, 33, 34, 35, 36, 38, 39, 42, 44, 45, 46, 48, 49, 50, 51, 52, 54, 55, 57, 58, 60, 62, 63, 64, 65, 66, 68, 69, 70, 72, 74, 75, 76, 77, 78, 80, 81, 82, 84, 85, 86, 87, 90, 91, 92, 93, 94, 95, 96, 98, 99, 100 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
All terms are nonprime numbers. Complement of A205523.
LINKS
EXAMPLE
Number 25 is in sequence because sigma(25)=31, gcd(25,31) = 1, and 31 mod 25 = 6.
MATHEMATICA
Select[Range[100], Mod[GCD[#, DivisorSigma[1, #]] - DivisorSigma[1, #], #] > 0 &] (* T. D. Noe, Feb 03 2012 *)
CROSSREFS
Sequence in context: A288862 A274584 A210998 * A125493 A341615 A164923
KEYWORD
nonn
AUTHOR
Jaroslav Krizek, Jan 28 2012
EXTENSIONS
Corrected by T. D. Noe, Feb 03 2012
STATUS
approved

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Last modified April 15 05:10 EDT 2024. Contains 371667 sequences. (Running on oeis4.)