The Art Deco style has been popular in the 3rd and the 4th decades of the 20th century and influenced by motifs of the ancient Egypt, because of the discovery in the early 1920s of the tomb of Tutankhamun. The number 3 was a magical number of the ancient Egyptians and was used extensively in Art Deco design, shown in decorative elements grouped/ reverberating in three. This door design from the 1930s Bucharest shows wonderfully the popularity of that “rule”.
Valentin Mandache, architectural historian 