A073130 a(n) = gcd(p(n+1) - p(n), p(p(n+1)) - p(p(n))), where p(n) is the n-th prime.

1, 2, 2, 2, 2, 2, 2, 4, 2, 2, 6, 2, 2, 4, 6, 6, 2, 6, 2, 2, 2, 2, 6, 8, 2, 2, 4, 2, 2, 2, 2, 2, 2, 2, 2, 6, 6, 4, 2, 2, 2, 2, 2, 2, 2, 4, 4, 4, 2, 4, 2, 2, 2, 6, 6, 6, 2, 2, 4, 2, 2, 2, 4, 2, 2, 2, 6, 2, 2, 2, 6, 4, 6, 6, 2, 6, 4, 2, 2, 2, 2, 2, 2, 6, 2, 6, 4, 2, 2, 4, 4, 2, 4, 2, 2, 2, 12, 2, 6, 2, 2, 2, 6, 2

Offset: 1

Author

Labos Elemer, Jul 16 2002

Keywords

• nonn

Links

• G. C. Greubel, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A073131, A073132.

Programs

Magma

[GCD(NthPrime(n+1) - NthPrime(n), NthPrime(NthPrime(n+1)) - NthPrime(NthPrime(n))): n in [1..120]]; // G. C. Greubel, Oct 20 2019

Maple

seq(gcd(ithprime(n+1) - ithprime(n), ithprime(ithprime(n+1)) - ithprime(ithprime(n))), n=1..120); # G. C. Greubel, Oct 20 2019

Mathematica

Table[GCD[Prime[n+1]-Prime[n], Prime[Prime[n+1]]-Prime[Prime[n]]], {n, 120}]

PARI

vector(120, n, gcd(prime(n+1) - prime(n), prime(prime(n+1)) - prime(prime(n))) ) \\ G. C. Greubel, Oct 20 2019

Sage

[gcd(nth_prime(n+1) - nth_prime(n), nth_prime(nth_prime(n+1)) - nth_prime(nth_prime(n))) for n in (1..120)] # G. C. Greubel, Oct 20 2019