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A118580
Least k such that 10^n + k is a Sophie Germain prime and the lesser of a twin prime pair.
0
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
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
KEYWORD
nonn
AUTHOR
Pierre CAMI, May 07 2006
STATUS
approved