a(n) = floor((Pi/2)^n).

Terms

a(0) =1a(1) =1a(2) =2a(3) =3a(4) =6a(5) =9a(6) =15a(7) =23a(8) =37a(9) =58a(10) =91a(11) =143a(12) =225a(13) =354a(14) =556a(15) =874a(16) =1373a(17) =2157a(18) =3389a(19) =5324a(20) =8363a(21) =13137a(22) =20636a(23) =32415a(24) =50918a(25) =79982a(26) =125636a(27) =197349a(28) =309996a(29) =486941