358017domain: NAppears in sequencesa(n) = 4*a(n-1) - a(n-2) + 1, with a(0) = 0, a(1) = 2.at n=10A001571Numbers k with property that there is an m = m(k) such that m(m+1)/2 divides k(k+1)/2 and m(k) > m(i) for all i < k.at n=33A309423