Is there an analytical description of the NACA 642-015A profile?
This report seems to include a reference to an analytical description of 6-series airfoils



On your second question: found this reference in Synthesis Of Subsonic Airplane Design by E. Torenbeek:


  A modification to the standard series is the A-series in which the sharp trailing edge angle is replaced by a larger one, resulting from straight contours which run from 80% chord backwards.


The paragraph contains a reference to "Theoretical and experimental data for a number of NACA 64-series airfoil sections" which turns out to be NACA LM R6J01