82355domain: NAppears in sequencesNumber of nonisomorphic commutative idempotent groupoids.at n=5A030257Triangle read by rows: T(n,k) is the number of commutative groupoids with n elements and k idempotents.at n=20A038021Numbers, p, that generate the prime quadruplets p^2-2p+2k (for k = -2, -1, 1, 2).at n=12A247882