OFFSET
1,1
COMMENTS
The harmonic mean of the divisors of k is k*A000005(k)/A000203(k). a(n) for n > 1 is a harmonic number, a term of A001599. Is the sequence finite ?
Similar sequences are obtained for other values of a(1). E.g. a(1) = 5 gives 5, 140, 496, 164989440, 28103080287744; a(1) = 8 gives 8, 672, 183694492800, 7322605472000.
LINKS
Takeshi Goto, Table of A001599(n) for n=1..937
EXAMPLE
The smallest number with harmonic mean of divisors = 2 is 6, hence a(2) = 6.
The next number with harmonic mean of divisors in {2, 6} is 270, hence a(3) = 270.
CROSSREFS
KEYWORD
nonn,hard,more
AUTHOR
Jaroslav Krizek, Aug 27 2009
EXTENSIONS
Edited and listed terms verified (using Takeshi Goto's list) by Klaus Brockhaus, Sep 04 2009
STATUS
approved