a(2n) = concatenation of 4n+1 and 4n+2, a(2n+1) = concatenation of the two most nearly equal numbers whose product is a(2n).

A068517

a(2n) = concatenation of 4n+1 and 4n+2, a(2n+1) = concatenation of the two most nearly equal numbers whose product is a(2n).