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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
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
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
KEYWORD
nonn,more
AUTHOR
Yasutoshi Kohmoto, Sep 05 2006
STATUS
approved