[seqfan] Re: nonpowers in A001481
N. J. A. Sloane
njas at research.att.com
Sat Jan 15 19:07:58 CET 2011
> I am tempted to submit a sequence as follows:
"Numbers that are the sum of 2 nonnegative squares
and not perfect powers."
2, 5, 10, 13, 17, 18, 20, 26, 29, 34, 37, 40, 41, 45, 50, 52, 53, 58, 61, 65, 68, ...
Does that seem to be a good idea?
Me: Yes! You might mention that these are the set-difference Athis \ Athat.
Also that these are the numbers n = 2^i Product_{p == 3 mod 4} p^2j Product_{p == 1 mod 4 } p^k
where gcd{i, 2j's, k's} = 1
Neil
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