a(0)=1; a(n) = sigma_2(n) + sigma_3(n).

Terms

a(0) =1a(1) =2a(2) =14a(3) =38a(4) =94a(5) =152a(6) =302a(7) =394a(8) =670a(9) =848a(10) =1264a(11) =1454a(12) =2254a(13) =2368a(14) =3346a(15) =3788a(16) =5022a(17) =5204a(18) =7268a(19) =7222a(20) =9744a(21) =10132a(22) =12598a(23) =12698a(24) =17230a(25) =16402a(26) =20632a(27) =21260a(28) =26162a(29) =25232