In this note, we determine the order of growth of the number of positive integers n \le x such that \lambda(n) is a sum of two square numbers, where \lambda(n) is the Carmichael function.
Carmichael function, sum of two squares
BANKS, WILLIAM D. and GÜLOĞLU, AHMET M.
"Values of the Carmichael Function Equal to a Sum of Two Squares,"
Turkish Journal of Mathematics: Vol. 33:
1, Article 2.
Available at: https://journals.tubitak.gov.tr/math/vol33/iss1/2