login
A143394
Least prime p such that p*(p + prime(n)) -+ 1 are twin primes, or 0 if no such prime exists.
2
0, 3, 0, 2, 3, 2, 3, 2, 109, 1291, 3, 557, 211, 3, 3, 7, 7, 3, 2, 13, 2, 5, 43, 97, 2, 3, 149, 43, 5, 3, 5, 13, 3, 2, 7, 3, 5, 197, 13, 73, 7, 11, 229, 23, 3, 5, 3, 23, 13, 2, 19, 7, 5, 109, 283, 67, 7, 3, 11, 13, 2, 43, 2, 19, 233, 7, 1061, 3, 3, 149, 43, 421, 11, 113, 29, 7, 991, 41, 61
OFFSET
1,2
COMMENTS
No twin primes of the form p*(p+2) -+ 1 for p prime.
Only one pair of twin primes of the form p*(p+3) -+ 1 (it occurs at p=3).
No twin primes of the form p*(p+5) -+ 1 for p prime.
EXAMPLE
3*(3+3) - 1 = 17 and 3*(3+3) + 1 = 19 are twin primes (and 2*(2+3) - 1 = 9 and 2*(2+3) + 1 = 11 are not twin primes) so a(2)=3.
CROSSREFS
Cf. A143393.
Sequence in context: A032531 A301430 A328311 * A112455 A001608 A159977
KEYWORD
nonn
AUTHOR
Pierre CAMI, Aug 12 2008
EXTENSIONS
Edited by Jon E. Schoenfield, Jan 19 2019
STATUS
approved