*Originally posted by David113*

**9^(9^(9^(9^...))), with 100 exponentiations, or
**

(...(((9!)!)!)!...), with 100 factorials?

Putting it another way, what is bigger - a(100) where a(0)=9 and a(n+1)=9^a(n), or b(100) where b(0)=9 and b(n+1)=b(n)! ?

OK I'll start over. Taks the first 9^9 compared to 9

9*9*9*9*9*9*9*9*9 = 387 420 489

9*8*7*6*5*4*3*2*1 = 362 880

(The above can be done using Google)

Now compare 387 420 489^9 to 362 880!

That's 1.9662705 e77 which is BIG, and ...

See http://en.wikipedia.org/wiki/Stirling%27s_approximation

... a number somewhat larger than (n/e)^n where n = 362,880 and e ~2.71828183

which is about 1 e4^n

which tacks on "00000" to "1" n+1 times.

Meaning the scientific notation is about 1 e(10000*362,880)

which is HUGE.

And it keeps going that way.

But maybe there's another OOPS coming.