Answer is:

>! 32

Search google for the remaining numbers in the sequence:
>! https://goo.gl/oTOCNA

Which gives 
>! The labels of [Interstate higways][1]. With both sequences one gets 1,2,3,4,5,6,7,8...

Image added:
>! [![enter image description here][2]][2]


  [1]: https://en.wikipedia.org/wiki/Interstate_Highway_System
  [2]: https://i.sstatic.net/KKfUI.png