357449732641domain: NAppears in sequencesa(n) = ((3^n - 1)*(3^n + 1))^2/2^(7 - (n mod 2)).at n=7A152258Base-9 representation of a(n) is the concatenation of the base-9 representations of 1, 2, ..., n, n-1, ..., 1.at n=7A260859