549754765312domain: NAppears in sequencesa(n) = 2^(n+2)*(2^(n+1)-1).at n=18A059153Nonunitary perfect numbers: k is the sum of its nonunitary divisors; i.e., k = sigma(k) - usigma(k).at n=6A064591Cogrowth sequence of the 16-element quasihedral group SD16 = <S,T | S^8, T^2, STS^5T>.at n=21A377885