for the first operation, a sequence where you add to get to the next term is expressed using the second operation, for example: 2, 4, 6, 8, you add by two to get to the next term of the sequence and it can be expressed using the second operation as 2x, a sequence where you multiply to get to the next term, the second operation, would be expressed using the third operation. for example: 2, 4, 8, 16, you multiply by 2 to get to the next term of the sequence, second operation and the sequence would be expressed as 2^x, third operation, as you can see, there is a pattern, if the sequence increases by operation n then it is expressed with operation n + 1, yet this pattern doesn't continue, exponentiation, the third operation, can be expressed in terms of exponentiation, for example: 4, 16, 256, 65536 increases by exponentiation, you square the term to get the next term, yet this sequence can be expressed as 2^(2^x), this is weird, why can it be expressed by exponentiation? is exponentiation the limit?