Deduction is a process of reasoning in which we explain the logicality of one statement with the help of others. Or in other words, several statements or premises help us to make a certain conclusion. In order to find the n-th element in some ordered set we should find and understand the relationship between the element, between the first and the second, between the second and the third...and so on. So , finding these relations we can conclude what is the n-th element and that is a process of deduction.