He kept working until few hours before his death. At his bed side there were 12 pages of equations. The final line of the last page is the equation shown below.
Albert Einstein archives reside at http://alberteinstein.info/ which is maintained by the Hebrew University of Jerusalem.
The digitized document that contains the last equation is known as the “Last Writing Pad” (archival call number: 3-12)
and click on the image. The viewer will show you many pages of equations contained in the writing pad that was found at Einstein’s bed side at the time of his death. The equation I show above can be found on the last page of the document known as the “Last Writing Pad.”
My sincere hope is that his final notes inspire someone and spark a new idea.
Update: Last time I checked I could not access the “Last Writing Pad” (archival call number: 3-12). I hope this is just a glitch and it is corrected quickly. The digitized archives are supposed to be open to public.