A104164 Sophie Germain type primes where 5*Prime[n]=2*Prime[m]+1.

7, 17, 47, 107, 167, 197, 257, 317, 347, 557, 677, 827, 947, 1097, 1217, 1307, 1367, 1427, 1607, 1847, 1877, 2027, 2207, 2267, 2297, 2417, 2477, 2657, 2927, 3257, 3557, 3617, 3677, 3917, 3947, 4157, 4397, 4457, 4877, 4967, 5507, 5717, 5867, 5927, 6257

Offset: 1

Author

Roger L. Bagula, Mar 10 2005

Keywords

• nonn

Crossrefs

Cf. Sophie Germain primes: A005384.

Programs

Mathematica

a = Delete[Union[Table[If [PrimeQ[(5*Prime[n] - 1)/2] == True, (5*Prime[n] - 1)/2, 0], {n, 1, 1000}]], 1]

Formula

a(n) = If (5*Prime[n]-1)/2 is prime, then a[m]=(5*Prime[n]-1)/2