Difference between 2^n and largest square strictly less than 2^n.

Terms

a(0) =1a(1) =1a(2) =3a(3) =4a(4) =7a(5) =7a(6) =15a(7) =7a(8) =31a(9) =28a(10) =63a(11) =23a(12) =127a(13) =92a(14) =255a(15) =7a(16) =511a(17) =28a(18) =1023a(19) =112a(20) =2047a(21) =448a(22) =4095a(23) =1792a(24) =8191a(25) =7168a(26) =16383a(27) =5503a(28) =32767a(29) =22012