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 A167797 Numbers with primitive root 10. 21
 7, 17, 19, 23, 29, 47, 49, 59, 61, 97, 109, 113, 131, 149, 167, 179, 181, 193, 223, 229, 233, 257, 263, 269, 289, 313, 337, 343, 361, 367, 379, 383, 389, 419, 433, 461, 487, 491, 499, 503, 509, 529, 541, 571, 577, 593, 619, 647, 659, 701, 709, 727, 743, 811 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Numbers n such that the decimal expansion of 1/n has period phi(n). For example, 1/49 has period 42. LINKS Vincenzo Librandi, Table of n, a(n) for n = 1..1000 MATHEMATICA pr=10; Select[Range[2, 2000], MultiplicativeOrder[pr, # ] == EulerPhi[ # ] &] CROSSREFS Cf. A001913 (primes with primitive root 10) Sequence in context: A323746 A101240 A191070 * A001913 A270387 A071845 Adjacent sequences:  A167794 A167795 A167796 * A167798 A167799 A167800 KEYWORD nonn AUTHOR T. D. Noe, Nov 12 2009 STATUS approved

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Last modified January 22 05:19 EST 2022. Contains 350481 sequences. (Running on oeis4.)