Number of primes <= 3^n.

Terms

a(0) =0a(1) =2a(2) =4a(3) =9a(4) =22a(5) =53a(6) =129a(7) =327a(8) =847a(9) =2227a(10) =5968a(11) =16097a(12) =43934a(13) =120739a(14) =334349a(15) =931260a(16) =2607165a(17) =7332159a(18) =20700806a(19) =58648288a(20) =166677978a(21) =475023803a(22) =1357200840a(23) =3886548158a(24) =11152818693a(25) =32064929886a(26) =92349038518a(27) =266398236486a(28) =769616513836