2600640domain: NAppears in sequencesTriangle of the numbers of different forests of m rooted trees of smallest order 2, i.e., without isolated vertices, on N labeled nodes.at n=38A105819A Jacobsthal number related number triangle.at n=48A110321k-imperfect numbers for some k >= 1.at n=21A1277243-imperfect numbers.at n=13A127726