9075135299domain: NAppears in sequencesNumber of combinations of n things from 1 to n at a time, with repeats allowed.at n=17A030662A054525 * A000984.at n=18A134764a(n) = binomial(2*n-2, n-1) + (-1)^n.at n=18A286033a(n) = Sum_{d|n} mu(n/d) * binomial(n+d-2, n-1).at n=18A332470