Successive numerators of Wallis's approximation to Pi/2 (reduced).

Terms

a(0) =1a(1) =2a(2) =4a(3) =16a(4) =64a(5) =128a(6) =256a(7) =2048a(8) =16384a(9) =32768a(10) =65536a(11) =262144a(12) =1048576a(13) =2097152a(14) =4194304a(15) =67108864a(16) =1073741824a(17) =2147483648a(18) =4294967296a(19) =17179869184a(20) =68719476736a(21) =137438953472a(22) =274877906944