Sources with direct knowledge tell us ... those who remained in O.J.'s inner circle flew into Vegas over the last week to see him before he passed. Unclear exactly how many friends, or who showed up, but we're told a handful of people came to Sin City and got to see O.J.

We're told Simpson was communicating just fine and was able to talk with his pals ... but, our sources say they all knew the end was coming, and that this would be their last chance to get some face time.

As we reported ... Simpson's family announced his death via his Twitter, saying he was surrounded by family and asking for privacy at this time.

News of O.J.'s cancer diagnosis broke in February ... though Simpson himself didn't address the cancer report head-on at the time -- instead saying he wasn't yet in hospice and ignoring questions about the disease itself.

While we don't know who showed up to say goodbye to O.J. -- frankly, a lot of his former famous friends had abandoned him post-murder trial acquittal -- we do know he was still close with his former Bills teammate Al Cowlings (A.C.) who drove in the Bronco.

No word on whether O.J. and A.C. remained close in these later years ... but A.C. had his back through and in the immediate aftermath of the mid-'90s legal saga.

It goes without saying, Simpson was incredibly controversial ... ending his NFL career as one of the greatest running backs of all time and going on to a popular movie career -- before his arrest and trial in the murders of Nicole Brown Simpson and Ron Goldman.

Even after the jury acquitted him, questions about his guilt still lingered ... and, many of his former colleagues quickly distanced themselves from Simpson.

That said, some of O.J.'s friends, we're told, stuck around ... and, they got the chance to reminiscence with him on his deathbed.