$1.99: Numerus

Price: $3.99 $1.99 until first 1,000 downloads 

A note from Balazs Faludi, the maker of Numerus: Even though existing users love my app, the downloads are dropping constantly. I hope this sale will help to make it better known.

Numerus is a sophisticated scientific calculator designed especially for iPhone and iPod touch.
It allows you to enter an expression the way as you would write it on a paper.
Just like a tape calculator Numerus preserves your calculating history. Simply scroll back to previous results or entries to reuse them – just with a single tap of your finger.
You can also save any results into 26 variables (A-Z) for later use.