61699domain: NAppears in sequencesNumber of asymmetric permutation rooted trees with n nodes.at n=13A005355Strong pseudoprimes to base 45.at n=15A020271a(n) = (2*n-1)*(n^2 -n +2)/2.at n=39A063488Nonprime numbers n such that phi(n) divides n^2 - 1, where phi(n) (A000010) is Euler's totient function.at n=21A098271