Number of irregular primes less than or equal to the 2^n-th prime.

Terms

a(0) =0a(1) =0a(2) =0a(3) =1a(4) =6a(5) =16a(6) =47a(7) =96a(8) =206a(9) =406a(10) =823a(11) =1626a(12) =3244a(13) =6454a(14) =12798a(15) =25715a(16) =51779a(17) =103315a(18) =206649a(19) =412883a(20) =825395a(21) =1650179a(22) =3299610a(23) =6600347a(24) =13201348a(25) =26403834