Uh oh! Wolfram|Alpha doesn't run without JavaScript.
Please enable JavaScript. If you don't know how, you can find instructions
here
.
Once you've done that, refresh this page to start using Wolfram|Alpha.
PA com a_1 = 100 and r = -7 . Calcola a_(15)
PA com a_1 = 100 and r = -7 . Calcola a_(15)
Natural Language
Math Input
Extended Keyboard
