24662841844domain: NAppears in sequencesa(2n) = a(2n-1) + 3a(2n-2), a(2n+1) = 2a(2n) + 3a(2n-1).at n=26A002537a(n) = ((4 + sqrt(7))^n + (4 - sqrt(7))^n)/2.at n=13A146964