A243310 Smallest k such that both prime(k)*prime(k+1) +/- 2^n are prime, or 0 if no such k exists.

1, 2, 2, 2, 0, 3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0

Offset

0,2

Comments

a(n) = 0 for n > 5?

a(n) = 0 for 5 < n <= 10000. Heuristics suggest that there are no other nonzero terms. - Charles R Greathouse IV, Jun 04 2014

Links

Table of n, a(n) for n=0..86.

Example

a(0) = 1 because prime(1)*prime(1+1)-2^0 = 5 and prime(1)*prime(1+1) + 2^0 = 7 are prime,
a(1) = 2 because prime(2)*prime(2+1)-2^1 = 13 and prime(2)*prime(2+1)+2^1 = 17 are prime,
a(2) = 2 because prime(2)*prime(2+1)-2^2 = 11 and prime(2)*prime(2+1)+2^2 = 19 are prime,
a(3) = 2 because prime(2)*prime(2+1)-2^3 = 7 and prime(2)*prime(2+1)+2^3 = 23 are prime.

Crossrefs

Cf. A006094.

Sequence in context: A059288 A319109 A217670 * A197727 A176884 A308361

Adjacent sequences: A243307 A243308 A243309 * A243311 A243312 A243313

Keyword

nonn,less

Author

Juri-Stepan Gerasimov, Jun 03 2014

Status

approved