A129780 The prime(n)-th lower twin prime.

5, 11, 29, 59, 137, 179, 239, 281, 431, 641, 809, 1031, 1151, 1277, 1427, 1667, 1931, 1997, 2141, 2339, 2549, 2789, 3119, 3359, 3581, 3851, 3929, 4091, 4157, 4259, 5009, 5279, 5639, 5657, 6359, 6551, 6779, 7127, 7349, 7757, 8231, 8387, 9011, 9239, 9431

Offset

1,1

Links

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

Formula

a(n) = A001359(A000040(n)). - Andrew Howroyd, Sep 12 2024

Example

The first prime is 2. The 2nd lower twin prime is 5, which gives the first entry.

Mathematica

Module[{maxp=50, tp}, tp=Select[Partition[Prime[Range[maxp*Prime[maxp]]], 2, 1], #[[2]] - #[[1]]==2&][[All, 1]]; Table[tp[[n]], {n, Prime[ Range[ maxp]]}]] (* Harvey P. Dale, Aug 06 2018 *)

Prog

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

Crossrefs

Cf. A000040, A001359, A129781.

Sequence in context: A107135 A036062 A201600 * A154504 A106060 A237642

Adjacent sequences: A129777 A129778 A129779 * A129781 A129782 A129783

Keyword

easy,nonn,changed

Author

Cino Hilliard, May 17 2007

Status

approved