A072303 Numbers n for which n is congruent to n^2 mod phi(n).

1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 12, 13, 16, 17, 18, 19, 21, 23, 24, 25, 27, 28, 29, 31, 32, 36, 37, 41, 43, 47, 48, 49, 53, 54, 59, 61, 64, 67, 71, 72, 73, 79, 81, 83, 89, 96, 97, 101, 103, 107, 108, 109, 112, 113, 121, 125, 127, 128, 131, 137, 139, 144, 149, 151, 157

Offset

1,2

Comments

Or, numbers n such that phi(n) divides n*(n-1). - Mohammed Bouayoun (mohammed.bouayoun(AT)sanef.com), Apr 14 2006

Links

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

Example

9 is in the sequence because phi(9) = 6. 9 % 6 = 3 and 9^2 % 6 = 3. But 10 is not in the sequence because phi(10) = 4 and 10 % 4 = 6 and 10^2 % 4 = 0.

Prog

(PARI) isok(n) = ((n^2 - n) % eulerphi(n)) == 0 \\ Michel Marcus, Jun 07 2013

Crossrefs

Cf. A000010, A068494.

Sequence in context: A055201 A213006 A068998 * A242413 A243068 A342339

Adjacent sequences: A072300 A072301 A072302 * A072304 A072305 A072306

Keyword

easy,nonn

Author

Igor Naverniouk (igor(AT)lexansoft.com), Jul 14 2002

Status

approved