The 3^n-th irregular prime.

Terms

a(0) =37a(1) =67a(2) =233a(3) =467a(4) =1307a(5) =4637a(6) =15601a(7) =54437a(8) =184279a(9) =616391a(10) =2009011a(11) =6568151a(12) =21341821a(13) =68826689a(14) =220682383a(15) =704456869