68719345664domain: NAppears in sequencesNumbers k such that ud(k)*phi(k) = sigma(k), ud(k) = A034444.at n=14A063903Even perfect numbers divided by 2.at n=6A133028a(n) = 6*a(n-1) - 8*a(n-2) for n > 1; a(0) = 3, a(1) = 14.at n=17A171499Numerators of the positive solution to 2^(n-1) = Sum_{d|n} a(d) * a(n/d).at n=37A299151