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Search: id:A110175
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| A110175 |
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Composite numbers n such that the equation phi(n)=phi(k)+phi(n-k) has no solution, where phi is Euler's totient function. |
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+0
2
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| 6, 30, 49, 81, 91, 95, 115, 121, 155, 187, 205, 210, 221, 243, 254, 259, 287, 298, 299, 329, 341, 355, 361, 377, 403, 415, 437, 451, 469, 473, 502, 533, 551, 559, 565, 611, 625, 629, 649, 655, 662, 667, 674, 679, 685, 703, 713, 731, 737, 746, 767, 779, 781
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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The only prime for which this equation has a solution is 3.
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MATHEMATICA
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a[n_] := Select[Range[n-1], EulerPhi[n]==EulerPhi[n-# ]+EulerPhi[ # ]&]; t=Table[Length[a[n]], {n, 1000}]; Complement[Flatten[Position[t, 0]], Prime[Range[PrimePi[1000]]]]
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CROSSREFS
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Cf. A110173 (least k such that phi(n)=phi(k)+phi(n-k)).
Sequence in context: A090126 A100194 A070195 this_sequence A014203 A044083 A024406
Adjacent sequences: A110172 A110173 A110174 this_sequence A110176 A110177 A110178
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KEYWORD
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nonn
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AUTHOR
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T. D. Noe (noe(AT)sspectra.com), Jul 15 2005
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