Text this: The Möbius function of separable and decomposable permutations ☆ [☆] Jelínek and Steingrímsson were supported by grant No. 090038012 from the Icelandic Research Fund. Jelínek was also supported by grant Z130-N13 from the Austrian Science Foundation (FWF). Jelínková was supported by project 1M0021620838 of the Czech Ministry of Education.