Its good practice to hide unnessesary content from the Sitefinity Lucene indexer. It's hard enough to find things IN lucene you don't want the results cluttered with like you menu or footer content.

Here's the answer courtesy of Nikola Zagorchev

DetectIndexRenderingMVCFeather.cshtmlView on GitHub
@using Telerik.Sitefinity.Frontend.Mvc.Infrastructure.Controllers;
 
@if (ViewContext.Controller.GetIndexRenderMode() == Telerik.Sitefinity.Web.UI.IndexRenderModes.Normal)
{
      <div>FROM LAYOUT</div>
}