151232990208domain: NAppears in sequencesa(n) is the number of coverings of 1..n by cyclic words of length n, such that each value from 1 to n appears precisely 3 times. That is, the union of all the letters in all of the words of a given covering is the multiset {1,1,1,2,2,2,...,n,n,n}. Repeats of words are not allowed in a given covering.at n=9A110105