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

Author

Rémy Sigrist, Sep 13 2019

Keywords

• nonn

Comments

This sequence has similarities with A008336 and with A008338.

Examples

			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
		

Links

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

Crossrefs

See A327442 for an additive variant.

Cf. A000010, A008336, A008338, A336823.

Programs

PARI

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