Jordan's totient function

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Let be a positive integer. In number theory, Jordan's totient function of a positive integer is the number of -tuples of positive integers all less than or equal to that form a coprime -tuple together with . (A tuple is coprime if and only if it is coprime as a set.) This is a generalisation of Euler's totient function, which is . The function is named after Camille Jordan.


For each , Jordan's totient function is multiplicative and may be evaluated as

, where ranges through the prime divisors of .


which may be written in the language of Dirichlet convolutions as[1]

and via Möbius inversion as


Since the Dirichlet generating function of is and the Dirichlet generating function of is , the series for becomes


and by inspection of the definition (recognizing that each factor in the product over the primes is a cyclotomic polynomial of ), the arithmetic functions defined by or can also be shown to be integer-valued multiplicative functions.

  • .      [2]

Order of matrix groups[edit]

The general linear group of matrices of order over has order[3]

The special linear group of matrices of order over has order

The symplectic group of matrices of order over has order

The first two formulas were discovered by Jordan.


Explicit lists in the OEIS are J2 in OEISA007434, J3 in OEISA059376, J4 in OEISA059377, J5 in OEISA059378, J6 up to J10 in OEISA069091 up to OEISA069095.

Multiplicative functions defined by ratios are J2(n)/J1(n) in OEISA001615, J3(n)/J1(n) in OEISA160889, J4(n)/J1(n) in OEISA160891, J5(n)/J1(n) in OEISA160893, J6(n)/J1(n) in OEISA160895, J7(n)/J1(n) in OEISA160897, J8(n)/J1(n) in OEISA160908, J9(n)/J1(n) in OEISA160953, J10(n)/J1(n) in OEISA160957, J11(n)/J1(n) in OEISA160960.

Examples of the ratios J2k(n)/Jk(n) are J4(n)/J2(n) in OEISA065958, J6(n)/J3(n) in OEISA065959, and J8(n)/J4(n) in OEISA065960.


  1. ^ Sándor & Crstici (2004) p.106
  2. ^ Holden et al in external links The formula is Gegenbauer's
  3. ^ All of these formulas are from Andrici and Priticari in #External links


  • L. E. Dickson (1971) [1919]. History of the Theory of Numbers, Vol. I. Chelsea Publishing. p. 147. ISBN 0-8284-0086-5. JFM 47.0100.04.
  • M. Ram Murty (2001). Problems in Analytic Number Theory. Graduate Texts in Mathematics. 206. Springer-Verlag. p. 11. ISBN 0-387-95143-1. Zbl 0971.11001.
  • Sándor, Jozsef; Crstici, Borislav (2004). Handbook of number theory II. Dordrecht: Kluwer Academic. pp. 32–36. ISBN 1-4020-2546-7. Zbl 1079.11001.

External links[edit]