A117848 Least K such that K*p(n)#-1 is the first of twin primes and 2*(K*p(n)#-1)+1 is prime, so K*p(n)#-1 is the first of twin primes and a Sophie Germain prime.

2, 1, 1, 2, 5, 9, 17, 11, 4, 16, 61, 118, 141, 680, 37, 430, 401, 576, 885, 953, 358, 1857, 1376, 91, 798, 209, 3014, 5707, 2327, 3013, 923, 9437, 403, 9392, 356, 3161, 266, 2012, 2796, 4095, 6362, 3008, 12227, 18277, 25353, 3682, 18414, 21783, 1889

Offset

1,1

Links

Table of n, a(n) for n=1..49.

Example

2*2-1 = 3, 3 5 twin primes and 2*3+1=7 prime, so 3 is the first of twin primes and is also a Sophie Germain prime.

Crossrefs

Sequence in context: A216396 A273488 A334955 * A025242 A356696 A163982

Adjacent sequences: A117845 A117846 A117847 * A117849 A117850 A117851

Keyword

nonn

Author

Pierre CAMI, May 01 2006

Status

approved