[seqfan] Re: phi-antipalindromic numbers

Douglas McNeil mcneil at hku.hk
Mon Sep 6 02:44:38 CEST 2010

[FWIW, I find 25983 such phi-antipalindromic numbers less than 10^6,
and I agree with Hans' half-sequence. They have a cute pattern,
probably related to the observations in the comments.]

Ideally good sequence invention abilities would go with good sequence
implementation abilities, but it doesn't always work out that way.

ISTM though that many sequences are of the sort "all non-prime
positive integers such that phi(2*n+1) < n", i.e. numbers satisfying
some straightforward constraint.  These don't even count as
programming, and our non-programming friends shouldn't fear them: it
honestly takes less time to write a one-line "program" than it does to
write an email about it.


Department of Earth Sciences
University of Hong Kong

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