Denominators of lower primes-only best approximates (POBAs) to Pi; see Comments.

Terms

a(0) =2a(1) =5a(2) =7a(3) =11a(4) =13a(5) =17a(6) =31a(7) =61a(8) =71a(9) =241a(10) =311a(11) =1427a(12) =1667a(13) =3023a(14) =4591a(15) =5749a(16) =9817a(17) =14563a(18) =15241a(19) =19309a(20) =43717a(21) =51853a(22) =56599a(23) =170701a(24) =177481a(25) =183809a(26) =184487a(27) =193979a(28) =194431a(29) =265381