0,1

The Gcc with Gmp program is at the bottom of the link. The link also has a PARI bisection algorithm which gives a very good approximation for the n-th prime number and the n-th twin prime number. For example the 10^10-th lower twin prime approximation is 6100475249386, this has a relative error of 0.000000698... from the actual a(10) above.

The (10^n)-th upper twin prime is given as a(n)+2 = (5,109,3823,79561, 1260991,18409201,252427603,...). - M. F. Hasler, Dec 06 2008

Cino Hilliard, Approximating the n-th lower twin prime (broken link)

a(n) = A001359(10^n). - M. F. Hasler, Dec 06 2008

For n=1, the first 10 lower twin primes (A001359) are: 3,5,11,17,29,41,59,71,101,107. So a(1) = 107 is the 10th lower twin prime.

Cf. A001097, A001359, A147797.

Sequence in context: A023325 A094200 A003705 * A261997 A362056 A061308

Adjacent sequences: A146211 A146212 A146213 * A146215 A146216 A146217

nonn,more

Cino Hilliard, Oct 28 2008

a(0) from Zak Seidov, Oct 29 2008

Edited and cross-references added by M. F. Hasler, Dec 06 2008

approved