Yes, it largely depends on your layout, but ads on index page won't hurt either. Its occasionally the best place to put up ads if the home page is content rich. Remember, homepage encounters for most impressions and advertisers will compete for ad space on homepage if your website is content rich, relevant and highly ranked....
It depends on what your site if for. Are you building it just for revenue? If so than yes, put Adsense on the index page.
I suggest you should put ads on the index page as you surely will get traffic on the home page. If you don't but ads on home page, then you are missing some amount of earnings for sure.
Adsense ads are a must on the index page especially when it is brimming with good contents and most of the time, the visitors land on the index page.