A094752 Largest k such that 2n/k + 1 as well as 2nk+1 are prime, or 0 if no such number exists.

2, 4, 6, 2, 10, 6, 14, 16, 9, 20, 1, 24, 26, 7, 5, 8, 0, 36, 0, 40, 21, 2, 1, 24, 5, 13, 54, 56, 1, 30, 0, 4, 66, 0, 7, 36, 74, 0, 1, 20, 1, 84, 0, 4, 90, 0, 94, 8, 0, 1, 1, 0, 1, 27, 110, 28, 0, 116, 0, 120, 0, 124, 126, 0, 130, 66, 134, 1, 1, 5, 0, 72, 146, 37, 150, 0, 0, 156, 0, 160, 9

Offset

1,1

Comments

For n=7 the largest k is 14 since 2*7/14+1=2 is prime and 2*7*14+1=197 which is also prime.

Links

Table of n, a(n) for n=1..81.

Crossrefs

Cf. A094753.

Cf. A005574.

Sequence in context: A352599 A373902 A242593 * A214061 A260300 A182291

Adjacent sequences: A094749 A094750 A094751 * A094753 A094754 A094755

Keyword

nonn

Author

Amarnath Murthy, May 29 2004

Extensions

Corrected by R. Piyo (nagoya314(AT)yahoo.com), Dec 10 2004

More terms from Franklin T. Adams-Watters, Nov 20 2006

Status

approved