287492domain: NAppears in sequencesNumbers n such that n through n+8 are divisible by the same number of distinct primes.at n=30A045937Number of idempotent 4X4 0..n matrices of rank 3.at n=31A224335G.f. A(x) satisfies: A( x - A(x^4)/x^2 ) = x.at n=12A272461