a(n) = sigma() [A000203] applied n times to prime(n).

Terms

a(0) =3a(1) =7a(2) =28a(3) =60a(4) =360a(5) =1512a(6) =3276a(7) =16256a(8) =65528a(9) =261120a(10) =79360a(11) =1098240a(12) =13852800a(13) =25261824a(14) =79536128a(15) =1040179456a(16) =1710858240a(17) =13815410400a(18) =71687577600a(19) =137707384824a(20) =151060010112