Fixed power operation on indicies
Fixed power operation on indicies to allow for power on rows. See #14973 

 - [ ] closes #14973
 - [ ] tests added / passed
 - [ ] passes ``git diff upstream/master | flake8 --diff``
 - [ ] whatsnew entry

## [Current coverage](https://codecov.io/gh/pandas-dev/pandas/pull/14981?src=pr) is 84.66% (diff: 100%)
> Merging [#14981](https://codecov.io/gh/pandas-dev/pandas/pull/14981?src=pr) into [master](https://codecov.io/gh/pandas-dev/pandas/branch/master?src=pr) will increase coverage by **<.01%**

```diff
@@             master     #14981   diff @@
==========================================
  Files           144        144          
  Lines         51056      51057     +1   
  Methods           0          0          
  Messages          0          0          
  Branches          0          0          
==========================================
+ Hits          43225      43226     +1   
  Misses         7831       7831          
  Partials          0          0          
```

> Powered by [Codecov](https://codecov.io?src=pr). Last update [aba7d25...6c793ed](https://codecov.io/gh/pandas-dev/pandas/compare/aba7d255a165bbc221be106839c59a876655c0c2...6c793ed8147e230eb3859828e44b31d6feeb444c?src=pr) this needs a test & a whatsnew note in 0.20.0 Will work on it! Closed this pull request and updated it with #14996 there is no reason to open another PR for the same issue. you just push to the same one. fine that you already did this.