Significance: a(n+1)-1 is the count of numbers < primorial(n+1) which have the largest prime divisor <= prime(n). e.g. a(5) = 39 is the index of 210=2*3*5*7 in A090958. which means there are 38 numbers of the form 2^a*3^b*5^c < 210. Can some one derive a general formula (asymptotic)?