[seqfan] Computationally hard sequence with four known terms

Felix Fröhlich felix.froe at gmail.com
Fri Jun 3 16:25:46 CEST 2016

I wonder, would the following sequence be okay to submit:

omega(2^(2^p-1)-1) for p = A000043(n).

i.e., a(n) = A001221(A000225(A000668(n))).

So far the sequence seems to have only four known terms, a(1)-a(4): 1, 1,
1, 1

Four terms seems okay, but they are not very distinct. The next Double
Mersenne number has two known factors according to
http://www.doublemersennes.org/factors.php and
http://www.mersenneforum.org/showpost.php?p=248215&postcount=41, but the
complete factorization is apparently unknown.

Felix Fröhlich

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