850500domain: NAppears in sequencesa(1)=2. a(n) = the smallest positive multiple of a(n-1) that is > a(n-1) and has the same number of 0's as 1's in its binary representation.at n=7A143147a(n) = Sum_{k=1..n-1} k^7 * sigma(k) * sigma(n-k).at n=5A259695