198180864domain: NAppears in sequencesMain diagonal of the table of k-almost primes (A078840): a(n) = (n+1)-st integer that is an n-almost prime.at n=24A078841a(n) = n*(n-3)*2^(n-2).at n=21A178987For n > 2 , a(n) = a(n-2) + lcm(a(n-2), n-1) with a(1)=2, a(2)=2.at n=28A217662