a(n) = 1 + sigma(n)^4.

Terms

a(0) =2a(1) =82a(2) =257a(3) =2402a(4) =1297a(5) =20737a(6) =4097a(7) =50626a(8) =28562a(9) =104977a(10) =20737a(11) =614657a(12) =38417a(13) =331777a(14) =331777a(15) =923522a(16) =104977a(17) =2313442a(18) =160001a(19) =3111697a(20) =1048577a(21) =1679617a(22) =331777a(23) =12960001a(24) =923522a(25) =3111697a(26) =2560001a(27) =9834497a(28) =810001a(29) =26873857