A070320 a(n) = Max( phi(k) : k=1..n ).

1, 1, 2, 2, 4, 4, 6, 6, 6, 6, 10, 10, 12, 12, 12, 12, 16, 16, 18, 18, 18, 18, 22, 22, 22, 22, 22, 22, 28, 28, 30, 30, 30, 30, 30, 30, 36, 36, 36, 36, 40, 40, 42, 42, 42, 42, 46, 46, 46, 46, 46, 46, 52, 52, 52, 52, 52, 52, 58, 58, 60, 60, 60, 60, 60, 60, 66, 66, 66, 66, 70, 70

Offset: 1

Author

Benoit Cloitre, May 11 2002

Keywords

• easy
• nonn

Crossrefs

Cf. A007917.

Programs

Mathematica

Module[{nn=80,ep},ep=EulerPhi[Range[nn]];Table[Max[Take[ep,n]],{n,nn}]] (* Harvey P. Dale, Jul 23 2023 *)
a[n_] := NextPrime[n + 1, -1] - 1; a[1] = 1; Array[a, 100] (* Amiram Eldar, May 08 2025 *)

PARI

a(n) = if(n == 1, 1, precprime(n) - 1); \\ Amiram Eldar, May 08 2025

Formula

a(1) = 1; for n >= 2, a(n) = A007917(n)-1.