Numbers k such that k divides 20^k - 1.

Terms

a(0) =1a(1) =19a(2) =361a(3) =6859a(4) =130321a(5) =2476099a(6) =47045881a(7) =148305659a(8) =893871739a(9) =2817807521a(10) =4234136149a(11) =10350100679a(12) =16983563041a(13) =53538342899a(14) =80448586831a(15) =196651912901a(16) =322687697779a(17) =815211156289