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 Prime

 http://functions.wolfram.com/13.03.06.0008.01

 Input Form

 Prime[n] == 2 + Sum[1 - Floor[PrimePi[k]/n], {k, 2, Floor[2 n Log[n] + 2]}]

 Standard Form

 Cell[BoxData[RowBox[List[RowBox[List["Prime", "[", "n", "]"]], "\[Equal]", RowBox[List["2", "+", RowBox[List[UnderoverscriptBox["\[Sum]", RowBox[List["k", "=", "2"]], RowBox[List["\[LeftFloor]", RowBox[List[RowBox[List["2", "n", " ", RowBox[List["Log", "[", "n", "]"]]]], "+", "2"]], "\[RightFloor]"]]], RowBox[List["(", RowBox[List["1", "-", RowBox[List["\[LeftFloor]", FractionBox[RowBox[List["PrimePi", "[", "k", "]"]], "n"], "\[RightFloor]"]]]], ")"]]]]]]]]]]

 MathML Form

 prime ( n ) 2 + k = 2 2 n log ( n ) + 2 ( 1 - π TagBox["\[Pi]", PrimePi] ( k ) n ) prime n 2 k 2 2 n n 2 1 -1 PrimePi k n -1 [/itex]

 Rule Form

 Cell[BoxData[RowBox[List[RowBox[List["HoldPattern", "[", RowBox[List["Prime", "[", "n_", "]"]], "]"]], "\[RuleDelayed]", RowBox[List["2", "+", RowBox[List[UnderoverscriptBox["\[Sum]", RowBox[List["k", "=", "2"]], RowBox[List["Floor", "[", RowBox[List[RowBox[List["2", " ", "n", " ", RowBox[List["Log", "[", "n", "]"]]]], "+", "2"]], "]"]]], RowBox[List["(", RowBox[List["1", "-", RowBox[List["Floor", "[", FractionBox[RowBox[List["PrimePi", "[", "k", "]"]], "n"], "]"]]]], ")"]]]]]]]]]]

 Date Added to functions.wolfram.com (modification date)

 2002-12-18