This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A129539 #9 May 25 2025 20:43:24
%S A129539 256,1296,4096,6561,10000,20736,38416,46656,50625,65536,104976,160000,
%T A129539 194481,234256,262144,331776,390625,456976,531441,614656,810000,
%U A129539 1000000,1048576,1185921,1336336,1500625,1679616,2085136,2313441
%N A129539 Composite numbers to composite powers.
%C A129539 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 A129539 The sequence starts with 256, because 256 is the smallest composite number to the smallest composite power.
%t A129539 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 A129539 Cf. A113877 - Semiprimes to semiprime powers - is a subsequence of this sequence.
%K A129539 nonn
%O A129539 0,1
%A A129539 _Tanya Khovanova_, May 29 2007