A119653 Denominator of BernoulliB[2p] divided by 6, where p=Prime[n].

5, 7, 11, 1, 23, 1, 1, 1, 47, 59, 1, 1, 83, 1, 1, 107, 1, 1, 1, 1, 1, 1, 167, 179, 1, 1, 1, 1, 1, 227, 1, 263, 1, 1, 1, 1, 1, 1, 1, 347, 359, 1, 383, 1, 1, 1, 1, 1, 1, 1, 467, 479, 1, 503, 1, 1, 1, 1, 1, 563, 1, 587, 1, 1, 1, 1, 1, 1, 1, 1, 1, 719, 1, 1, 1, 1, 1, 1, 1, 1, 839, 1, 863, 1, 1

Offset: 1

Author

Alexander Adamchuk, Jul 28 2006

Keywords

• nonn

Comments

a(n) is equal to 1 or a safe prime p: (p-1)/2 is also prime, A005385[n] = 5,7,11,23,47,59,83,107,167,179,227,263,347,359,383,467,479,503,563,587,719,839,863,887,983,1019... The indices of primes in a(n) are n=1,2,3,5,9,10,13,16,23,24..=A072192[n] Indices of Sophie Germain primes: p and 2p+1 are primes.

Crossrefs

Cf. A002445, A005385, A072192, A005384, A079148.

Programs

Mathematica

Table[Denominator[BernoulliB[2Prime[n]]]/6,{n,1,100}]

Formula

a(n) = Denominator[BernoulliB[2Prime[n]]]/6.