129644789domain: NAppears in sequencesCatalan numbers - 1.at n=15A001453a(n) = Sum_{k|n} mu(k)*Catalan(n/k) (mu = Moebius function A008683).at n=16A002996a(n) = C(n)-1+0^n where C(n) = A000108(n).at n=17A141364