Posted by JR on Monday, October 29, 2012 at 12:36am.
for 30 days on the 1st daY I GET A PENNY THAN ON IT DUOBLES EVERY DAY UNTIL DAY 30
HOW MUCH PENNIES DO I HAVE ON DAY30

MATH  Steve, Monday, October 29, 2012 at 1:18am
just take a look at the number of pennies on day #n
n #
1 1
2 2
3 4
4 8
...
n 2^(n1)
so, on day 30 you have 2^29 pennies
That's about $5.4 million. You could retire and spend the rest of your life counting them! 
MATH  eric, Monday, December 7, 2015 at 8:28am
1000000000