Fourth power of primes of the form 4k+1 (A002144).

Terms

a(0) =625a(1) =28561a(2) =83521a(3) =707281a(4) =1874161a(5) =2825761a(6) =7890481a(7) =13845841a(8) =28398241a(9) =62742241a(10) =88529281a(11) =104060401a(12) =141158161a(13) =163047361a(14) =352275361a(15) =492884401a(16) =607573201a(17) =895745041a(18) =1073283121a(19) =1387488001a(20) =1506138481a(21) =2750058481