492882domain: NAppears in sequencesIntegers x such that for some integer y we have uphi(x) = uphi(y) = x-y, where uphi(n) = A047994(n) is the unitary totient function: If n = Product p_i^e_i, uphi(n) = Product (p_i^e_i - 1).at n=31A067739Number of 4k+1 primes (A002144) in range ]2^n,2^(n+1)].at n=23A095007