Denominators of a series expansion for Pi/2.

Terms

a(0) =1a(1) =2a(2) =6a(3) =-20a(4) =-24a(5) =-56a(6) =144a(7) =160a(8) =352a(9) =-832a(10) =-896a(11) =-1920a(12) =4352a(13) =4608a(14) =9728a(15) =-21504a(16) =-22528a(17) =-47104a(18) =102400a(19) =106496a(20) =221184a(21) =-475136a(22) =-491520a(23) =-1015808a(24) =2162688a(25) =2228224a(26) =4587520a(27) =-9699328a(28) =-9961472a(29) =-20447232