17651846030domain: NAppears in sequencesA threes sequence that gets more even factors out: a(n) = (3^n - 1)*(3^n + 1)/2^(4 - (n mod 2)).at n=12A152299a(n) = (n*3^(n+1)+((5*3^(n+1)+(-1)^(n))/4))/4.at n=19A191008