HarmonicNumber[n] == HarmonicNumber[n, 1]

Cell[BoxData[RowBox[List[RowBox[List["HarmonicNumber", "[", "n", "]"]], "\[Equal]", RowBox[List["HarmonicNumber", "[", RowBox[List["n", ",", "1"]], "]"]]]]]]

<math xmlns='http://www.w3.org/1998/Math/MathML' mathematica:form='TraditionalForm' xmlns:mathematica='http://www.wolfram.com/XML/'> <semantics> <mrow> <msub> <semantics> <mi> H </mi> <annotation-xml encoding='MathML-Content'> <ci> HarmonicNumber </ci> </annotation-xml> </semantics> <mi> n </mi> </msub> <mo> &#10869; </mo> <msubsup> <semantics> <mi> H </mi> <annotation-xml encoding='MathML-Content'> <ci> HarmonicNumber </ci> </annotation-xml> </semantics> <mi> n </mi> <mrow> <mo> ( </mo> <mn> 1 </mn> <mo> ) </mo> </mrow> </msubsup> </mrow> <annotation-xml encoding='MathML-Content'> <apply> <eq /> <apply> <ci> HarmonicNumber </ci> <ci> n </ci> </apply> <apply> <ci> HarmonicNumber </ci> <ci> n </ci> <cn type='integer'> 1 </cn> </apply> </apply> </annotation-xml> </semantics> </math>

Cell[BoxData[RowBox[List[RowBox[List["HoldPattern", "[", RowBox[List["HarmonicNumber", "[", "n_", "]"]], "]"]], "\[RuleDelayed]", RowBox[List["HarmonicNumber", "[", RowBox[List["n", ",", "1"]], "]"]]]]]]

2001-10-29