Numbers k that divide s(k), where s(1)=1, s(j)=21*s(j-1)+j.

Terms

a(0) =1a(1) =3a(2) =5a(3) =7a(4) =15a(5) =21a(6) =25a(7) =35a(8) =75a(9) =105a(10) =125a(11) =175a(12) =301a(13) =375a(14) =525a(15) =625a(16) =875a(17) =903a(18) =1389a(19) =1505a(20) =1875a(21) =2625a(22) =3125a(23) =3165a(24) =4375a(25) =4417a(26) =4515a(27) =6945a(28) =7525a(29) =9375