Let a(1)=1; for n>1, a(n)=nextprime((Pi/2)*a(n-1)).

Terms

a(0) =1a(1) =2a(2) =5a(3) =11a(4) =19a(5) =31a(6) =53a(7) =89a(8) =149a(9) =239a(10) =379a(11) =599a(12) =941a(13) =1481a(14) =2333a(15) =3671a(16) =5779a(17) =9091a(18) =14281a(19) =22433a(20) =35251a(21) =55373a(22) =86981a(23) =136649a(24) =214651a(25) =337189a(26) =529657a(27) =832003a(28) =1306913a(29) =2052899