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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

Table of n, a(n) for n=1..65.

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

Cf. A000203, A000040, A009194, A054024, A205524, A205525.

Sequence in context: A288862 A274584 A210998 * A125493 A341615 A164923

Adjacent sequences:  A205521 A205522 A205523 * A205525 A205526 A205527

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 January 29 05:09 EST 2022. Contains 350672 sequences. (Running on oeis4.)