A143428 a(n)=least prime == -1 mod 6 such that q(n)*(q(n)+a(n))-1 and q(n)*(q(n)+a(n))+1 are twin primes with q(i)=i-th prime == 1 mod 6.

53, 11, 11, 11, 17, 53, 197, 227, 11, 53, 17, 53, 23, 17, 179, 269, 47, 311, 17, 11, 59, 41, 11, 53, 137, 11, 83, 53, 59, 17, 47, 17, 11, 47, 173, 269, 23, 101, 11, 137, 443, 53, 107, 263, 11, 23, 251, 17, 137, 383, 479, 353, 107, 173, 71, 197, 17, 107, 101, 179, 89, 17

Offset

1,1

Links

Pierre CAMI, Table of n, a(n) for n = 1..10000

Example

q(1)=7, 7*(7+5)-1=83 prime but 85 composite
7*(7+11)-1=125 composite
7*(7+17)-1=167 prime but 169 composite
7*(7+23)-1=209 composite
7*(7+29)-1=251 prime but 253 composite
7*(7+41)-1=335 composite
7*(7+47)-1=377 composite
7*(7+53)-1=419 419 and 421 twin primes so a(1)=53

Crossrefs

Cf. A143427, A143429, A143430.

Sequence in context: A232126 A078681 A143294 * A143385 A231426 A298061

Adjacent sequences: A143425 A143426 A143427 * A143429 A143430 A143431

Keyword

nonn

Author

Pierre CAMI, Aug 14 2008

Status

approved