What's the name of the iOS / OS X calculator app that has 'variables' functionality? I'm looking for an app on the App Store but I forgot its name.

It is a calculator app that looks like it has been written on a noteblock.

You can store the solutions of calculations as quasi-variables and then reuse them later on.

I know it's available for the Mac and all iOS devices.

Does anyone know what app this is?
This sounds like the app Soulver which is available on Mac OS X and iOS.  It allows you to use a mixture of natural language and spreadsheet/calculator functions to perform easily readable equations.