A084311 a(n) = gcd(prime(n)-1,n-1).

1, 1, 2, 3, 2, 1, 2, 1, 2, 1, 10, 1, 4, 1, 2, 1, 2, 1, 6, 1, 4, 3, 2, 1, 24, 25, 2, 1, 4, 1, 6, 1, 8, 3, 2, 5, 12, 1, 2, 1, 2, 1, 2, 1, 4, 9, 2, 1, 2, 1, 2, 17, 4, 1, 2, 1, 4, 3, 2, 1, 6, 1, 2, 1, 8, 1, 66, 1, 2, 3, 2, 1, 6, 1, 2, 1, 4, 11, 2, 1, 2, 3, 2, 1, 6, 17, 2, 3, 4, 1, 2, 1, 2, 1, 2, 1, 4, 1, 2, 9, 2, 1

Offset: 1

Author

Labos Elemer, Jun 13 2003

Keywords

• nonn

Links

• Ivan Neretin, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A000040, A084309-A084316.

Programs

Mathematica

Table[GCD[Prime[w]-1, w-1], {w, 1, 128}]

PARI

a(n) = gcd(prime(n)-1, n-1); \\ Michel Marcus, May 04 2017