A066900 a(n) = max( {k : phi(k)==n (mod(k)) } ).

2, 6, 2, 12, 3, 18, 2, 30, 5, 22, 3, 42, 7, 10, 9, 60, 3, 54, 5, 66, 11, 46, 15, 90, 13, 6, 7, 58, 5, 62, 2, 120, 21, 14, 3, 126, 19, 30, 5, 150, 7, 98, 11, 138, 27, 94, 3, 210, 5, 34, 13, 106, 33, 162, 7, 174, 29, 118, 35, 198, 31, 14, 39, 240, 11, 134, 17, 46, 45, 142

Offset

1,1

Links

Table of n, a(n) for n=1..70.

Max Alekseyev, PARI/GP Scripts for Miscellaneous Math Problems: invphi.gp, 2005-2009.

Prog

(PARI) a(n) = {my(v = invphi(n), m = if (#v, vecmax(v), n)); vecmax(select(x->(Mod(eulerphi(x), x) == n), [1..m])); } \\ Michel Marcus, Feb 22 2021; needs invphi

Crossrefs

Cf. A000010, A014197, A066899.

Sequence in context: A292522 A243197 A319048 * A356016 A336852 A079462

Adjacent sequences: A066897 A066898 A066899 * A066901 A066902 A066903

Keyword

nonn

Author

Benoit Cloitre, Jan 24 2002

Extensions

More terms from Michel Marcus, Feb 22 2021

Status

approved