a(n) = number of primes between n^2 and n^4.

Terms

a(0) =0a(1) =0a(2) =4a(3) =18a(4) =48a(5) =105a(6) =199a(7) =342a(8) =546a(9) =825a(10) =1204a(11) =1685a(12) =2300a(13) =3068a(14) =4008a(15) =5143a(16) =6488a(17) =8091a(18) =9956a(19) =12115a(20) =14605a(21) =17446a(22) =20676a(23) =24322a(24) =28441a(25) =33004a(26) =38114a(27) =43805a(28) =50066a(29) =56951