A326889 a(1) = 1; thereafter a(n) = a(n-1) / phi(n) if phi(n) divides a(n-1), otherwise a(n) = a(n-1) * phi(n), where phi is the Euler phi-function A000010.

1, 1, 2, 1, 4, 2, 12, 3, 18, 72, 720, 180, 15, 90, 720, 90, 1440, 240, 4320, 540, 45, 450, 9900, 79200, 3960, 330, 5940, 495, 13860, 110880, 3696, 231, 4620, 73920, 3080, 36960, 1330560, 73920, 3080, 49280, 1232, 14784, 352, 7040, 168960, 7680, 353280, 22080

Offset

1,3

Comments

This sequence has similarities with A008336 and with A008338.

Links

Rémy Sigrist, Table of n, a(n) for n = 1..2500

Example

The first terms, alongside phi(n), are:
  n   a(n)  phi(n)
  --  ----  ------
   1     1       1
   2     1       1
   3     2       2
   4     1       2
   5     4       4
   6     2       2
   7    12       6
   8     3       4
   9    18       6
  10    72       4

Prog

(PARI) for (n=1, 48, print1 (v=if (n==1, 1, v%e=eulerphi(n), v*e, v/e) ", "))

Crossrefs

See A327442 for an additive variant.

Cf. A000010, A008336, A008338, A336823.

Sequence in context: A132280 A345734 A059970 * A309303 A245471 A352548

Adjacent sequences: A326886 A326887 A326888 * A326890 A326891 A326892

Keyword

nonn

Author

Rémy Sigrist, Sep 13 2019

Status

approved