A066813 a(n) = lcm(phi(n), phi(n+1)).

1, 2, 2, 4, 4, 6, 12, 12, 12, 20, 20, 12, 12, 24, 8, 16, 48, 18, 72, 24, 60, 110, 88, 40, 60, 36, 36, 84, 56, 120, 240, 80, 80, 48, 24, 36, 36, 72, 48, 80, 120, 84, 420, 120, 264, 506, 368, 336, 420, 160, 96, 312, 468, 360, 120, 72, 252, 812, 464, 240, 60, 180, 288, 96

Offset: 1

Author

Benoit Cloitre, Jan 20 2002

Keywords

• nonn
• easy

Links

• Harry J. Smith, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A000010 (phi), A058515, A083542.

Programs

Mathematica

LCM@@EulerPhi[#]&/@Partition[Range[100],2,1] (* Harvey P. Dale, May 07 2011 *)

PARI

a(n) = { lcm(eulerphi(n), eulerphi(n+1)) } \\ Harry J. Smith, Mar 29 2010

Formula

a(n) = A083542(n)/A058515(n). - Amiram Eldar, May 07 2025