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A219548
Smallest prime factor of 2^A219547(n) + 1.
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
1,1
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).
FORMULA
a(n) = A002586(A219547(n)).
CROSSREFS
Sequence in context: A086022 A125649 A219549 * A351865 A218723 A097736
KEYWORD
nonn
AUTHOR
Jonathan Sondow, Nov 24 2012
STATUS
approved