20-almost primes (generalization of semiprimes).

Terms

a(0) =1048576a(1) =1572864a(2) =2359296a(3) =2621440a(4) =3538944a(5) =3670016a(6) =3932160a(7) =5308416a(8) =5505024a(9) =5767168a(10) =5898240a(11) =6553600a(12) =6815744a(13) =7962624a(14) =8257536a(15) =8650752a(16) =8847360a(17) =8912896a(18) =9175040a(19) =9830400a(20) =9961472a(21) =10223616a(22) =11943936a(23) =12058624