Happy Bday Barack! As POTUS turns 51, take a look at back at some of his most memorable moments with famous friends
Beyonce and Jay-Z
The "Countdown" singer, in particular, has grown close with the Obamas. She sang at the President's Inaugural Ball in January 2009, and recently penned a sweet letter to Michelle Obama. "I am proud to have my daughter grow up in a world where she has people like you, to look up to," Blue Ivy's mama wrote.
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