A255367 a(n) = r^(p-2) mod p, where p is the n-th prime and r is the least positive primitive root of p.

1, 2, 3, 5, 6, 7, 6, 10, 14, 15, 21, 19, 7, 29, 19, 27, 30, 31, 34, 61, 44, 53, 42, 30, 39, 51, 62, 54, 91, 38, 85, 66, 46, 70, 75, 126, 63, 82, 67, 87, 90, 91, 181, 116, 99, 133, 106, 149, 114, 191, 78, 205, 69, 42, 86, 158, 135, 226, 111, 94, 189, 147, 123

Offset: 1

Author

Alois P. Heinz, May 04 2015

Keywords

• nonn
• look

Comments

a(n) is the last element of row n of A254309.

Links

• Alois P. Heinz, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A000040, A001918, A254309.

Programs

Maple

a:= n-> (p-> numtheory[primroot](p)&^(p-2) mod p)(ithprime(n)):
seq(a(n), n=1..70);

Mathematica

a[n_] := With[{p = Prime[n]}, Mod[PrimitiveRoot[p]^(p-2), p]]; Array[a, 70] (* Jean-François Alcover, Mar 24 2017 *)

Formula

a(n) = r^(p-2) mod p, with p = A000040(n) and r = A001918(n).