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

Terms

a(0) =2a(1) =5a(2) =7a(3) =13a(4) =53a(5) =67a(6) =137a(7) =179a(8) =181a(9) =197a(10) =353a(11) =1723a(12) =3319a(13) =5113a(14) =6469a(15) =9181a(16) =15269a(17) =17981a(18) =22727a(19) =24083a(20) =31541a(21) =34253a(22) =37643a(23) =46457a(24) =64763a(25) =67447a(26) =199403a(27) =531101a(28) =1791689a(29) =5175551