[seqfan] Iterating sigma - 1
franktaw at netscape.net
franktaw at netscape.net
Thu May 6 22:51:15 CEST 2010
Consider http://www.research.att.com/~njas/sequences/A039654 - Prime
reached by iterating f(x) = sigma(x)-1 on n.
It isn't obvious that this iteration always reaches a prime, although
it seems nearly certain that it does. Should we add something like ",
or 0 if no prime is ever reached", with a comment that apparently the
sequence always does reach a prime? (Or can someone prove that a prime
is always reached?)
One might, in this case, also add a(1) = 0 (suitably modifying the
comment).
Franklin T. Adams-Watters
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