A051547 a(n) = lcm{ phi(1), ..., phi(n) }, where phi is Euler's totient function A000010.

1, 1, 2, 2, 4, 4, 12, 12, 12, 12, 60, 60, 60, 60, 120, 120, 240, 240, 720, 720, 720, 720, 7920, 7920, 7920, 7920, 7920, 7920, 55440, 55440, 55440, 55440, 55440, 55440, 55440, 55440, 55440, 55440, 55440, 55440, 55440, 55440, 55440, 55440, 55440, 55440, 1275120, 1275120, 1275120

Offset: 1

Author

N. J. A. Sloane

Keywords

• nonn

Links

• Michael De Vlieger, Table of n, a(n) for n = 1..10000
• P. Moree, H. Roskam, On an arithmetical function related to Euler's totient and the discriminator, Fib. Quart. 33 (1995) 332-340.

Crossrefs

Cf. A000010, A076244 (distinct values), A076245 (n where a(n) > a(n-1)).

Programs

Mathematica

FoldList[LCM @@ {#1, EulerPhi@ #2} &, Range@ 44] (* Michael De Vlieger, Dec 09 2018 *)

PARI

a(n) = lcm(vector(n, k, eulerphi(k))); \\ Michel Marcus, Jul 30 2017

PARI

apply( A051547(n)=lcm(apply(eulerphi,[2..n])), [1..50]) \\ Defines the function A051547; apply(...) for check & example. - M. F. Hasler, Dec 09 2018