a(n) = sigma(a(n-1)) + phi(a(n-1)), a(1)=3.

Terms

a(0) =3a(1) =6a(2) =14a(3) =30a(4) =80a(5) =218a(6) =438a(7) =1032a(8) =2976a(9) =9024a(10) =27328a(11) =74512a(12) =181646a(13) =363294a(14) =908268a(15) =2422072a(16) =5752432a(17) =15203056a(18) =39044504a(19) =92788840a(20) =252556992a(21) =808096140a(22) =2666717760a(23) =10285934208a(24) =33734451200a(25) =97757260032a(26) =293143652800