Numbers k such that d(k)^4 divides k.

Terms

a(0) =1a(1) =625a(2) =6561a(3) =117649a(4) =4100625a(5) =31250000a(6) =37515625a(7) =73530625a(8) =771895089a(9) =1000000000a(10) =2147483648a(11) =6442450944a(12) =10737418240a(13) =15032385536a(14) =23622320128a(15) =25937424601a(16) =27917287424a(17) =32212254720a(18) =33059881728a(19) =36507222016a(20) =40802189312a(21) =45097156608a(22) =49392123904