1814760domain: NAppears in sequencesNumber of circular permutations of the multiset {1,1,2,2,...,n,n} (up to rotations) with odd distances between equal elements.at n=6A137730Sum of distinct terms of A002674: a(0) = 0, a(2n) = A255411(A153880(a(n))), a(2n+1) = 1+A255411(A153880(a(n))).at n=20A275959