a(n) = sigma(n^4).

Terms

a(0) =1a(1) =31a(2) =121a(3) =511a(4) =781a(5) =3751a(6) =2801a(7) =8191a(8) =9841a(9) =24211a(10) =16105a(11) =61831a(12) =30941a(13) =86831a(14) =94501a(15) =131071a(16) =88741a(17) =305071a(18) =137561a(19) =399091a(20) =338921a(21) =499255a(22) =292561a(23) =991111a(24) =488281a(25) =959171a(26) =797161a(27) =1431311a(28) =732541a(29) =2929531