Class numbers associated with terms of A001988.

Terms

a(0) =1a(1) =1a(2) =5a(3) =7a(4) =7a(5) =7a(6) =9a(7) =53a(8) =73a(9) =83a(10) =83a(11) =83a(12) =157a(13) =185a(14) =185a(15) =185a(16) =185a(17) =1927a(18) =2295a(19) =2273a(20) =5313a(21) =5313a(22) =7173a(23) =9529a(24) =18545a(25) =18545a(26) =18545a(27) =18545a(28) =22635a(29) =22635