For each positive integer k {\displaystyle k} , Jordan's totient function J k {\displaystyle J_{k}} is multiplicative and may be evaluated as
The first two formulas were discovered by Jordan.
Sándor & Crstici (2004) p.106 ↩
Holden et al in external links. The formula is Gegenbauer's. ↩
All of these formulas are from Andrica and Piticari in #External links. ↩