0,2

Instead of starting with a(0) = 1 for the first twin prime (3,5) other sequences can be formed for a(0) = 2, i.e. 2nd twin prime: 2, 5, 29, 641, 44381, 7212059, etc., a(0) = 4: 4, 17, 239, 12161, 1583927, etc., a(0) = 6: 6, 41, 1151, 93251, 16989317, etc., a(0) = 7: 7, 59 1931,176021, 35263691, etc., a(0) = 8: 8, 71, 2339,221201, 45749309 and so on.

Tomas Oliveira e Silva, Tables of values of pi(x) and of pi2(x) [From M. F. Hasler (MHasler(AT)univ-ag.fr), Mar 02 2009]

a(n+1) = A001359(a(n)); a(0)=1. [From M. F. Hasler (MHasler(AT)univ-ag.fr), Mar 02 2009]

a(3) = 137 because a(2) = 11 and the 11-th twin prime is (137,139).

Cf. A007097.

Sequence in context: A057205 A121897 A067657 this_sequence A072639 A100459 A010682

Adjacent sequences: A063499 A063500 A063501 this_sequence A063503 A063504 A063505

hard,nice,nonn

Lubomir Alexandrov (alexandr(AT)thsun1.jinr.ru), Jul 30 2001

Edited by Frank Ellermann, Jan 25, 2002

Offset and example corrected by Farideh Firoozbakht (mymontain(AT)yahoo.com), Dec 07 2008

a(7) = 65818751039 from Zak Seidov (zakseidov(AT)yahoo.com) and Farideh Firoozbakht (mymontain(AT)yahoo.com), Dec 13 2008

Computed a(8)=46091763604421 using data from T. Oliveira e Silva. M. F. Hasler (MHasler(AT)univ-ag.fr), Mar 02 2009