78181domain: NAppears in sequencesPartial sums of orders of finite perfect groups (A060793).at n=31A121513Numbers k such that k and k^2 use only the digits 1, 2, 6, 7 and 8.at n=11A137014Numbers k such that phi(k) = phi(k+1) + phi(k+2).at n=5A197112