Number of semiprimes s such that 2^n < s <= 2^(n+1).

Terms

a(0) =0a(1) =1a(2) =1a(3) =4a(4) =4a(5) =12a(6) =20a(7) =40a(8) =75a(9) =147a(10) =285a(11) =535a(12) =1062a(13) =2006a(14) =3918a(15) =7548a(16) =14595a(17) =28293a(18) =54761a(19) =106452a(20) =206421a(21) =401522a(22) =780966a(23) =1520543a(24) =2962226a(25) =5777162a(26) =11272279a(27) =22009839a(28) =43006972a(29) =84077384