Composites Of This Sequence

David Wilson dwilson at
Mon Aug 25 16:52:19 CEST 2008

Leroy Quet wrote:
> By the way,
> All terms of A037074 are included in the sequence of the composites of A143578.
> Are there any other composites?
> Thanks,
> Leroy Quet

Empirically, all of the elements of A143578 seem to have <= 2 prime 

If true, then A143578 has the following characterization:

A143578 = {1} U primes U {pq: p, q prime, p+q | p^2-1}

The latter set includes the products of twin primes A037074, as well as 
other composites, e.g, 5*19.

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