%N Squarefree product of all odd primes dividing n, and 1 if n is a power of 2: A099985/2.
%C There are no odd primes dividing n iff n is a power of 2.
%C This sequence coincides with the bisection of A007947 (even indices), which is A099985, dividing out the even prime 2 in the squarefree kernel.
%F a(n) = A099985(n)/2 = A007947(2*n)/2.
%F a(n) = A000265(A007947(n)) = A007947(A000265(n)). - From _Charles R Greathouse IV_, Jan 19 2012.
%e a(5)=5 because 5 is a single odd prime.
%e a(9)=3 because 9=3*3 has as squarefree part 3.
%e a(1)=1 because 1 is a power of 2, having no odd primes as a factor.
%Y Cf. A099985, A099984, A007947, A000265.
%A _Wolfdieter Lang_, Jan 19 2012