Sum of the divisors of 4^n+1.

Terms

a(0) =3a(1) =6a(2) =18a(3) =84a(4) =258a(5) =1302a(6) =4356a(7) =20520a(8) =65538a(9) =351120a(10) =1110276a(11) =5048232a(12) =17041416a(13) =82623888a(14) =284225796a(15) =1494039792a(16) =4301668356a(17) =20788904016a(18) =73234343952a(19) =332019460560