Nonprime numbers of the form 2^n - 1.

Terms

a(0) =0a(1) =1a(2) =15a(3) =63a(4) =255a(5) =511a(6) =1023a(7) =2047a(8) =4095a(9) =16383a(10) =32767a(11) =65535a(12) =262143a(13) =1048575a(14) =2097151a(15) =4194303a(16) =8388607a(17) =16777215a(18) =33554431a(19) =67108863a(20) =134217727a(21) =268435455a(22) =536870911a(23) =1073741823a(24) =4294967295a(25) =8589934591a(26) =17179869183a(27) =34359738367