A129781 The prime(n)-th upper twin prime.

7, 13, 31, 61, 139, 181, 241, 283, 433, 643, 811, 1033, 1153, 1279, 1429, 1669, 1933, 1999, 2143, 2341, 2551, 2791, 3121, 3361, 3583, 3853, 3931, 4093, 4159, 4261, 5011, 5281, 5641, 5659, 6361, 6553, 6781, 7129, 7351, 7759, 8233, 8389, 9013, 9241, 9433

Offset

1,1

Links

Table of n, a(n) for n=1..45.

Formula

a(n) = A006512(A000040(n)). - Andrew Howroyd, Sep 12 2024

Example

The first prime is 2. The 2nd upper twin prime is 7, which gives the first entry.

Mathematica

With[{twprs=Transpose[Select[Partition[Prime[Range[10000]], 2, 1], Last[#]- First[#] == 2&]][[2]]}, Flatten[Table[Take[twprs, {Prime[n]}], {n, 50}]]] (* Harvey P. Dale, Jul 25 2011 *)

Prog

(PARI) twinu(n) = { my(c=0, x=1); while(c<n, if(isprime(prime(x)+2), c++); x++; ); prime(x) }
a(n) = twinu(prime(n))

Crossrefs

Cf. A000040, A006512.

Sequence in context: A107146 A201601 A284353 * A174217 A040061 A289123

Adjacent sequences: A129778 A129779 A129780 * A129782 A129783 A129784

Keyword

easy,nonn

Author

Cino Hilliard, May 17 2007

Status

approved