A070076 Number of n-digit twin prime pairs.

2, 6, 27, 170, 1019, 6945, 50811, 381332, 2984194, 23988173, 196963369, 1646209172, 13964079652, 119945656793, 1041428920639, 9126986454994, 80644643655861, 717727049224277

Offset: 1

Author

Lekraj Beedassy, May 06 2002

Keywords

• hard
• more
• nonn
• base

Examples

			n=1: a(1)=2 pairs: (3,5), (5,7).
n=2: a(2)=6 pairs: (11,13), (17,19), (29,31), (41,43), (59,61), (71,73).
		

References

• Jean-Marie De Koninck, Armel Mercier: 1001 Problems in Classical Number Theory, American Mathematical Society, 2007 - from Eva-Maria Zschorn (e-m.zschorn(AT)zaschendorf.km3.de), Mar 23 2010
• Paulo Ribenboim: The New Book of Prime Number Records (3. Auflage), Springer-Verlag Berlin, 1996 - from Eva-Maria Zschorn (e-m.zschorn(AT)zaschendorf.km3.de), Mar 23 2010

Links

• Anonymous, Twin Prime Index(1 through 394000000)
• X. Gourdon & P. Sebah, Online computation of the first primes and twin primes up to 50000
• Tomás Oliveira e Silva, Tables of values of pi(x) and of pi2(x)

Crossrefs

Cf. A007508.

Formula

a(n) = A007508(n) - A007508(n-1) [From Max Alekseyev, Jun 16 2011]

Extensions

a(6) corrected by Harvey P. Dale, Sep 02 2008

a(9) corrected and a(15)-a(18) from Donovan Johnson, Apr 25 2010