Hello, I'd like to define a sequence in mathematica and let it go, but I'm not sure how to tell mathematica to look for the previous number in sequence and then derive the new one. Something like this, [tex] a_1, a_2, a_3, a_4, a_5 = [/tex] [tex] 3, 7, 23, 87, 343 = [/tex] [tex] 0+3, 3+4, 7+16, 23+64, 87+256 [/tex] where we start with 3 and add every previous number to the consecutive power of 4. Thanks, If you know, please tell as fast as you're able, I'd really need this today. Thanks ^ ∞ wait and something else, how to do this I have a function f.ex f(x) = log[x] but now I'd like to graph the functions f(f(f(f(f(x)))))) up to a certain number of times, for example 100 such functions and then give off all the values starting with x=10. Any ideas? PLease help me, I really need this, or otherwise I shall be tortured to the end of my little life.