Biunitary Divisor
A divisor 
of a positive integer 
is biunitary if the greatest common unitary divisor of 
and 
is 1. For a prime power 
, the biunitary divisors are the powers 1, 
, 
, ..., 
, except for 
when 
is even (Cohen 1990).
REFERENCES:
Cohen, G. L. "On an Integer's Infinitary Divisors." Math. Comput. 54, 395-411, 1990.
Suryanarayana, D. "The Number of Bi-Unitary Divisors of an Integer." The Theory of Arithmetic Functions (Proc. Conf., Western Michigan Univ., Kalamazoo, Mich., 1971. New York: Springer-Verlag, pp. 273-282, 1972.
Suryanarayana, D. and Rao, R. S. R. C. "The Number of Bi-Unitary Divisors of an Integer. II." J. Indian Math. Soc. 39, 261-280, 1975.
