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A081397
a(n) = least k such that GCD of sigma(k) = A000203(k) and phi(k) = A000010(k) equals n-th primorial = A002110(n).
1
3, 14, 488, 16072, 284229, 29221621, 25014312576
OFFSET
1,1
COMMENTS
a(8) <= 1524139588224. - Donovan Johnson, Dec 14 2009
FORMULA
a(n) = Min_{k : A081396(k) = A002110(n)}.
EXAMPLE
k=284229: sigma(284229) = 482790 = 2*3*5*7*11*19, phi(284229) = 166320 = 2*2*2*3*3*3*3*5*7*11, common factor set = {2,3,5,7,11}, gcd(sigma,phi) = 2310.
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Labos Elemer, Mar 28 2003
EXTENSIONS
a(6) corrected and a(7) from Donovan Johnson, Dec 14 2009
STATUS
approved