"September (Septembers herlige natur)" [Danish title] is number 1775 in the Hans Christian Andersen Center's register of Andersen's literary works, i.e. no. 275 in the category poems (the range 1501 - 2900). BFN 208.
"September (Septembers herlige natur)" [Danish title] was first published 18 December 1832, cf. the bibliographic description (in Danish) in : Digterens danske Værker 1822-1875, number in bibliography: 208:
September. (Septembers herlige Natur) p. 85
In modern Danish on p. 255 in Johan de Mylius (editor): H.C. Andersen. Samlede digte ('Collected poems', Copenhagen, 2000).