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 A386242 #6 Jul 23 2025 09:06:21
%S A386242 1,9,25,27,121,125,1521,2025,5625,24025,42875,59319,32761,393129,
%T A386242 851929,1540081,6275025,15327225,27258841,41925625,127893481,
%U A386242 243204025,385611769,268336125,1979449081,4823441401,12870221809,25698491351,51354402813,127506840561,205822820329
%N A386242 a(n) is the least perfect power A001597 with binary weight n.
%t A386242 upto = 10^11; L = Table[2 upto, {2 + Log2@ upto}]; Do[n = 1; While[(v = n^k) <= upto, nb = Plus @@ IntegerDigits[v, 2]; If[L[[nb]] > v, L[[nb]] = v]; n++], {k, 2, Log2[upto]}]; Take[L, Position[L, 2 upto][[1, 1]] - 1] (* _Giovanni Resta_, Jul 23 2025 *)
%Y A386242 Cf. A000120, A001597, A231897.
%K A386242 nonn,base
%O A386242 1,2
%A A386242 _Hugo Pfoertner_, Jul 23 2025
%E A386242 a(27)-a(31) from _Giovanni Resta_, Jul 23 2025