Installation view of Robert Indiana: Number Paintings at the Museum Haus Lange Krefeld, Germany, June 11–July 24, 1966. Left to right, Three (1965), Three (1964–65), and Four (1964–65). Photo: ©Kunstmuseen Krefeld–Artothek
Robert Indiana: Number Paintings was an exhibition of the artist's 60 x 50 inch and 24-inch square Number paintings.