A180172 a(n) = gcd(prime(n)+2, n).

1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 11, 3, 1, 1, 1, 1, 1, 9, 1, 1, 3, 1, 1, 1, 1, 1, 3, 1, 1, 5, 1, 1, 1, 1, 1, 9, 1, 1, 13, 5, 1, 3, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 1, 5, 11, 1, 1, 1, 1, 71, 1, 1, 1, 3, 1, 1, 3, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 15, 7, 1, 3, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1

Offset: 1

Author

Zak Seidov, Aug 15 2010

Keywords

• nonn

Links

• G. C. Greubel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A003989, A052147, A084309, A084310, A180173.

Programs

Magma

[GCD(n,NthPrime(n) +2): n in [1..110]]; // G. C. Greubel, Mar 12 2023

Mathematica

Table[GCD[n,Prime[n]+2],{n,200}]

SageMath

[gcd(nth_prime(n) + 2, n) for n in range(1,111)] # G. C. Greubel, Mar 12 2023