A128160 a(n) = least k such that the remainder when 20^k is divided by k is n.

19, 3, 17, 6, 15, 7, 13, 9, 11, 18, 7989, 92, 973, 33, 611, 24, 2661, 382, 559, 21, 96641237093, 42, 1887, 94, 155, 27, 60403, 36, 7971, 74, 1172954777, 46, 2470227509, 122, 45, 116, 1837, 362, 779, 60, 469, 358, 1275143, 51, 55, 118, 723, 49

Offset: 1

Author

Alexander Adamchuk, Feb 16 2007

Keywords

• hard
• nonn

Links

• Robert G. Wilson v, Table of n, a(n) for n = 1..10000 with -1 for large entries where a(n) has not yet been found

Crossrefs

Cf. A036236, A078457, A119678, A119679, A127816, A119715, A119714, A127817, A127818, A127819, A127820, A127821, A128154, A128155, A128156, A128157, A128158, A128159.

Cf. A128149, A128150.

Programs

Mathematica

t = Table[0, {10000} ]; k = 1; While[ k < 4000000000, a = PowerMod[20, k, k]; If[a < 10001 && t[[a]] == 0, t[[a]] = k; Print[{a, k}]]; k++ ]; t (* Robert G. Wilson v, Aug 04 2009 *)

Extensions

More terms copied from a-file by Hagen von Eitzen, Oct 22 2009