A072192 Indices of Sophie Germain primes: p and 2p+1 are primes.

1, 2, 3, 5, 9, 10, 13, 16, 23, 24, 30, 32, 40, 41, 43, 51, 52, 54, 60, 62, 72, 81, 83, 86, 94, 97, 108, 116, 119, 120, 124, 128, 132, 135, 140, 156, 162, 170, 171, 173, 176, 185, 200, 201, 209, 223, 228, 230, 234, 239, 240, 246

Offset

1,2

References

M. Abramowitz and I. A. Stegun, eds., Handbook of Mathematical Functions, National Bureau of Standards Applied Math. Series 55, 1964 (and various reprintings), p. 870.

J. Roberts, Lure of the Integers, Math. Assoc. America, 1992, p. 83.

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

M. Abramowitz and I. A. Stegun, eds., Handbook of Mathematical Functions, National Bureau of Standards, Applied Math. Series 55, Tenth Printing, 1972 [alternative scanned copy].

Formula

a(n) = A000720(A005384(n)). - Ridouane Oudra, Mar 07 2023

Example

5 is element of the sequence, P(5)=11 and 2*11+1=23 is prime.

Mathematica

Select[Range[250], PrimeQ[2Prime[#]+1]&] (* Harvey P. Dale, Feb 22 2017 *)

Crossrefs

Cf. A005384, A000720.

Sequence in context: A333607 A047370 A226820 * A287158 A325835 A050158

Adjacent sequences: A072189 A072190 A072191 * A072193 A072194 A072195

Keyword

easy,nonn

Author

Miklos Kristof, Jul 02 2002

Status

approved