A084310 a(n) = gcd(prime(n)+1, n).

1, 2, 3, 4, 1, 2, 1, 4, 3, 10, 1, 2, 1, 2, 3, 2, 1, 2, 1, 4, 1, 2, 1, 6, 1, 2, 1, 4, 1, 6, 1, 4, 3, 2, 5, 4, 1, 2, 3, 2, 1, 14, 1, 2, 9, 2, 1, 16, 1, 10, 3, 4, 1, 18, 1, 8, 3, 2, 1, 6, 1, 2, 7, 8, 1, 6, 1, 2, 3, 70, 1, 72, 1, 2, 5, 4, 1, 2, 1, 10, 3, 2, 1, 14, 5, 2, 3, 2, 1, 2, 13, 4, 1, 2, 5, 24, 1, 2, 1, 2

Offset: 1

Author

Labos Elemer, Jun 13 2003

Keywords

• nonn
• easy

Links

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

Crossrefs

Cf. A084309, A084311, A084312, A084313, A084314, A084315, A084316.

Programs

Maple

A084310:= n-> igcd(ithprime(n)+1,n): seq(A084310(n), n=1..150); # Wesley Ivan Hurt, Jan 27 2017

Mathematica

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

PARI

a(n) = gcd(prime(n)+1, n); \\ Michel Marcus, Jan 27 2017