ANSWER: 6


N(N-1)/2 for N=4 gives 4(4-1)/2 = 4(3)/2 = 12/2 = 6

OR

  Devers Evans Franklin Grant
Devers ---------- 1 2 3
Evans ---------- ---------- 4 5
Franklin ---------- ---------- ---------- 6
Grant ---------- ---------- ---------- ----------

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