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

Terms

a(0) =1a(1) =3a(2) =7a(3) =15a(4) =31a(5) =7a(6) =127a(7) =255a(8) =511a(9) =1023a(10) =2047a(11) =455a(12) =8191a(13) =16383a(14) =32767a(15) =65535a(16) =131071a(17) =29127a(18) =524287a(19) =41943a(20) =42799a(21) =4194303a(22) =8388607a(23) =1864135a(24) =33554431a(25) =67108863a(26) =134217727a(27) =268435455a(28) =536870911a(29) =119304647