138142domain: NAppears in sequences(1/1 - 1/3 + 1/6 + ... + d/C(n+1,2))*LCM{1,3,6,...,C(n+1,2)}, where d = (-1)^n.at n=11A025559Numbers k such that Euler phi(k) / Carmichael lambda(k) = 34.at n=27A066698