1,1

Numbers n such that the decimal expansion of 1/n has period phi(n). For example, 1/49 has period 42.

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

pr=10; Select[Range[2, 2000], MultiplicativeOrder[pr, # ] == EulerPhi[ # ] &]

Cf. A001913 (primes with primitive root 10)

Sequence in context: A323746 A101240 A191070 * A001913 A270387 A071845

Adjacent sequences: A167794 A167795 A167796 * A167798 A167799 A167800

nonn

T. D. Noe, Nov 12 2009

approved