Number of irreducible indecomposable permutations of degree n.

Terms

a(0) =0a(1) =1a(2) =1a(3) =1a(4) =7a(5) =15a(6) =31a(7) =63a(8) =127a(9) =255a(10) =511a(11) =1023a(12) =2047a(13) =4095a(14) =8191a(15) =16383a(16) =32767a(17) =65535a(18) =131071a(19) =262143a(20) =524287a(21) =1048575a(22) =2097151a(23) =4194303a(24) =8388607a(25) =16777215a(26) =33554431a(27) =67108863a(28) =134217727a(29) =268435455