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Composite numbers to composite powers.
1

%I #6 Mar 30 2012 18:49:09

%S 256,1296,4096,6561,10000,20736,38416,46656,50625,65536,104976,160000,

%T 194481,234256,262144,331776,390625,456976,531441,614656,810000,

%U 1000000,1048576,1185921,1336336,1500625,1679616,2085136,2313441

%N Composite numbers to composite powers.

%C Only unique powers are shown here. E.g., 4096 = 4^6 = 8^4, but 4096 is only in the sequence once. - Franklin T. Adams-Watters, Sep 28 2011

%e The sequence starts with 256, because 256 is the smallest composite number to the smallest composite power.

%t comp = Select[Range[2, 40], ! PrimeQ[ # ] &]; Select[ Union[Flatten[ Table[comp[[n]]^comp[[k]], {n, Length[comp]}, {k, Length[comp]}]]], # < comp[[Length[comp]]]^4 &]

%Y Cf. A113877 - Semiprimes to semiprime powers - is a subsequence of this sequence.

%K nonn

%O 0,1

%A _Tanya Khovanova_, May 29 2007