%I #17 Sep 05 2020 07:45:17

%S 1,3,7,15,31,7,127,255,511,1023,2047,455,8191,16383,32767,65535,

%T 131071,29127,524287,41943,42799,4194303,8388607,1864135,33554431,

%U 67108863,134217727,268435455,536870911,119304647,2147483647,4294967295,8589934591,17179869183,34359738367

%N Squarefree part of 2^n-1 : the smallest number such that a(n)*(2^n-1) is a square.

%H Amiram Eldar, <a href="/A069112/b069112.txt">Table of n, a(n) for n = 1..1206</a>

%F a(n) = A007913(A000225(n)). - _Michel Marcus_, Apr 10 2014

%t SquareFreePart[n_] := Times @@ Apply[Power, {First[#], Mod[Last[#], 2]}& /@ FactorInteger[n], {1}]; a[n_] := SquareFreePart[2^n-1]; Table[a[n], {n, 1, 32}] (* _Jean-François Alcover_, Apr 10 2014 *)

%o (PARI) for(n=1,60,print1(core(2^n-1),","))

%Y Cf. A000225, A007913.

%K nonn

%O 1,2

%A _Benoit Cloitre_, Apr 06 2002

%E More terms from _Amiram Eldar_, Sep 05 2020