The number of n-almost primes less than or equal to 4^n, starting with a(0)=1.

Terms

a(0) =1a(1) =2a(2) =6a(3) =13a(4) =34a(5) =77a(6) =177a(7) =406a(8) =887a(9) =1962a(10) =4225a(11) =9094a(12) =19482a(13) =41414a(14) =87706a(15) =184976a(16) =389357a(17) =816193a(18) =1708412a(19) =3566209a(20) =7431153a(21) =15457234a(22) =32098652a(23) =66560309a(24) =137830562a(25) =285062028a(26) =588871107a(27) =1215176367a(28) =2505048537a(29) =5159228725