A118580 Least k such that 10^n + k is a Sophie Germain prime and the lesser of a twin prime pair.

2, 1, 79, 19, 91, 361, 211, 1699, 1651, 2359, 3001, 26569, 61, 19759, 18109, 29911, 13741, 4381, 3811, 13429, 15469, 27331, 11431, 49111, 47929, 17041, 227971, 48979, 315511, 65299, 86359, 78049, 2449, 69949, 136579, 24781, 149779, 256171, 143551

Offset

0,1

Links

Table of n, a(n) for n=0..38.

Formula

a(n) = A118479(n+1) - 10^n.

Example

10^1 + 1 = 11; 11 is a Sophie Germain prime and 11 and 13 are twin prime pairs.

Mathematica

f[n_] := Block[{k = 10^(n - 1)}, While[ !PrimeQ[k] || !PrimeQ[k + 2] || !PrimeQ[2k + 1], k++ ]; k - 10^(n - 1)]; Array[f, 40] (* Robert G. Wilson v, May 13 2006 *)

Crossrefs

Cf. A118479.

Sequence in context: A096681 A247793 A067276 * A118558 A095837 A095835

Adjacent sequences: A118577 A118578 A118579 * A118581 A118582 A118583

Keyword

nonn

Author

Pierre CAMI, May 07 2006

Status

approved