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A121287 Numbers such that Sigma(n)*UnitarySigma(n) is divisible by UnitaryPhi(n)*n. 1
1, 6, 60, 140, 8190, 32760 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
No more terms up to 10^8. - Michel Marcus, Jan 24 2019
a(7) > 10^12, if it exists. - Giovanni Resta, Jun 07 2019
LINKS
FORMULA
{n: (n*A047994(n)) | (sigma(n)*A034448(n)) }.
PROG
(PARI) uphi(n) = my(f=factor(n)~); prod(i=1, #f, f[1, i]^f[2, i]-1); \\ A047994
usigma(n) = sumdivmult(n, d, if(gcd(d, n/d)==1, d)); \\ A034448
isok(n) = ((sigma(n)*usigma(n)) % (n*uphi(n))) == 0; \\ Michel Marcus, Jan 24 2019
CROSSREFS
Sequence in context: A337691 A126576 A232181 * A069072 A361761 A361787
KEYWORD
nonn,more
AUTHOR
Yasutoshi Kohmoto, Sep 05 2006
STATUS
approved

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Last modified March 29 05:16 EDT 2024. Contains 371264 sequences. (Running on oeis4.)