OFFSET
1,2
COMMENTS
Tau = A000005 is the number of divisors of its argument. rad(n) = A007947(n) is the product of the primes dividing n.
Note that rad() is idempotent: rad(rad(n)) = rad(n). - R. J. Mathar, Nov 07 2011
LINKS
Donovan Johnson, Table of n, a(n) for n = 1..496 (terms < 10^18)
EXAMPLE
288 is in the sequence because tau(288)= 18, tau(18)=6, rad(288)=6.
MAPLE
A010553 := proc(n)
numtheory[tau](numtheory[tau](n)) ;
end proc:
for n from 1 to 480000 do
printf("%d, ", n) ;
end if;
end do: # R. J. Mathar, Nov 07 2011
CROSSREFS
KEYWORD
nonn
AUTHOR
Michel Lagneau, Feb 23 2010
EXTENSIONS
Example corrected and edited by Michel Lagneau, Apr 25 2010
STATUS
approved