313713domain: NAppears in sequencesE.g.f. A(x) = exp(x+x^2+x^3+x^4+x^5+x^6).at n=8A193932Triangle read by rows: T(n,k) is the number of nilpotent subpermutations on an n-set, each of nilpotency index less than or equal to k.at n=42A261764a(n) = a(n-1) + a(n-2) + gcd(a(n-1), n), a(1) = a(2) = 1.at n=25A360884