A165768 Smallest prime factor of the semiprime 2^A165767(n)-A165767(n).

2, 11, 7, 2, 271, 6733, 41, 11, 2, 3769453, 77647, 2, 541, 1394161003757, 13806493, 5, 3, 1778463179021, 193, 19, 17377902756647509, 398407, 3, 389, 137, 137867, 3, 3, 160038737, 739, 4889866261929241, 37, 5, 48109, 3190436507

Offset: 1

Author

M. F. Hasler, Oct 08 2009

Keywords

• nonn

Comments

a(n)=2 whenever A165767(n) is even.

Examples

			17377902756647509 is in this sequence because it is the smallest prime factor of the semiprime 2^199-199.
		

Links

• Max Alekseyev, Table of n, a(n) for n = 1..39

Formula

a(n) = (2^A165767(n)-A165767(n))/A165769(n).

Extensions

More terms from Max Alekseyev, Dec 13 2011