A117508 Denominators of partial sums of the Brun series divided by 5.

3, 21, 3003, 969969, 872002131, 1537339756953, 5532885785273847, 28676947025074349001, 298326279901848452657403, 3479379402495258503343291189, 66257821961717207679166294112127

Offset: 1

Author

Wolfdieter Lang, Apr 13 2006

Keywords

• nonn
• easy
• frac

Comments

Numerators divided by 4 are given by A117507.

See A117507 for more information.

Formula

a(n)=denominator(r(n))/5, with r(n):=sum(1/ltp(k) + 1/(ltp(k)+2),k=1..n), n>=1, with ltp(k):=A001359(k) (lesser twin primes).