Limit number of (m-n)-almost-primes in range [2^m..2^{m+1}-1].

Terms

a(0) =2a(1) =5a(2) =8a(3) =22a(4) =47a(5) =103a(6) =234a(7) =493a(8) =1087a(9) =2282a(10) =4901a(11) =10427a(12) =21993a(13) =46389a(14) =97394a(15) =204567a(16) =427099a(17) =892587a(18) =1858338a(19) =3865692a(20) =8027140a(21) =16642918a(22) =34463760a(23) =71273199a(24) =147235636a(25) =303814862a(26) =626313383a(27) =1289883519a(28) =2654196000