A059787 Distance between 2*(n-th prime) and next prime.

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

Offset: 1

Author

Labos Elemer, Feb 22 2001

Keywords

• nonn

Comments

If a(n)=1 then prime(n) is a Sophie Germain prime.

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A005385, A005384.

Programs

Maple

with(numtheory): [seq(nextprime(2*ithprime(k))-2*ithprime(k),k=1..256)];

Mathematica

Table[n2=2Prime[n];NextPrime[n2]-n2,{n,110}] (* Harvey P. Dale, Jun 07 2012 *)

PARI

a(n) = my(pp=2*prime(n)); nextprime(pp) - pp; \\ Michel Marcus, Mar 22 2020