12164095domain: NAppears in sequencesa(n) = smallest number k such that k-1 and k+1 both have exactly n prime divisors (counted with multiplicity).at n=11A154704Least number k such that d(k-1) = d(k+1) = 2n or 0 if no such k exists, where d(n)=A000005(n).at n=21A190646