176360domain: NAppears in sequencesa(n) = 441*n^2 - 2*n.at n=19A157737Numbers m such that sigma(m)*tau(m) is a square but sigma(m)/tau(m) is not an integer.at n=38A327831a(n) = (1/(n+1)) * Sum_{k=0..n} (k+1)^5 * binomial(2*n-k,n-k).at n=7A390964