Number of primes between 3^n and 4^n.

Terms

a(0) =0a(1) =2a(2) =9a(3) =32a(4) =119a(5) =435a(6) =1573a(7) =5695a(8) =20773a(9) =76057a(10) =279850a(11) =1033937a(12) =3837070a(13) =14296494a(14) =53468768a(15) =200673056a(16) =755606952a(17) =2853697709a(18) =10807617884a(19) =41036410818a(20) =156186010430a(21) =595759180892