A219548 Smallest prime factor of 2^A219547(n) + 1.

257, 65537, 641, 257, 193, 257, 274177, 65537, 257, 641, 257, 449, 59649589127497217, 257, 257, 641, 65537, 257, 769, 257, 65537, 641, 257, 193, 257, 1238926361552897, 5441, 257, 257, 65537, 274177, 257, 193, 257, 641, 65537, 257, 59649589127497217, 257, 65537, 641, 257, 257, 274177, 65537, 257, 641, 257, 5953

Offset: 1

Author

Jonathan Sondow, Nov 24 2012

Keywords

• nonn

Comments

2p divides sigma_k(2p), where p = a(n) and k = A219547(n). But 2p is not the least m > 1 that divides sigma_k(m).

Crossrefs

Cf. A002586, A219547.

Formula

a(n) = A002586(A219547(n)).