Number of steps needed to reverse a pattern of length 2*n of cellular automaton Rule 90.

Terms

a(0) =1a(1) =3a(2) =7a(3) =7a(4) =31a(5) =63a(6) =15a(7) =15a(8) =511a(9) =63a(10) =2047a(11) =1023a(12) =511a(13) =16383a(14) =31a(15) =31a(16) =4095a(17) =87381a(18) =4095a(19) =1023a(20) =127a(21) =4095a(22) =8388607a(23) =2097151a(24) =255a(25) =67108863a(26) =1048575a(27) =511a(28) =536870911a(29) =1073741823