67977559domain: NAppears in sequencesa(n) = Sum_{k=1..7} n^k.at n=13A228291Numbers of the form p*q, where p is prime and q=(p^k-1)/(p-1) is also prime for some integer k>1.at n=29A330832Numbers k in A024619 such that all residues r (mod k) in row k of A381801 are such that rad(r) divides k, where rad = A007947.at n=31A382438