Sum of the divisors of 3^n+1.

Terms

a(0) =3a(1) =7a(2) =18a(3) =56a(4) =126a(5) =434a(6) =1332a(7) =3836a(8) =10476a(9) =42560a(10) =109926a(11) =315112a(12) =816732a(13) =2790074a(14) =8906760a(15) =30220288a(16) =64570086a(17) =229156928a(18) =706911048a(19) =2034690952a(20) =5357742012a(21) =21838961760a(22) =56496274632a(23) =164750562956a(24) =456919958880