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A097651
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a(n) is the earliest number m such that n*pi(m)=phi(m).
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0
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2, 11, 37, 169, 917, 1087, 15407, 10379, 30451, 64591, 187063, 498419, 1304707, 3523969, 9558541, 26042629, 73134517, 189963073, 528839387, 1394194181, 3779851321, 10246935931, 27800769133, 75370121689
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OFFSET
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1,1
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COMMENTS
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It seems that for each n, a(n) exists and the set An={m|n*pi(m)=phi(m)} is finite, for example A1={2,3,4,8,10,14,20,90}(elements of A1 are terms of the sequence A037171), A2={11,13,27,39,63,122,124, 136,152,176,224,322,364,410,460,1086,1164,3432,3612},... . According to the definition, a(n) is the smallest element of An. For n<19, 3 doesn't divide a(n), is this true for all terms of the sequence?
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LINKS
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FORMULA
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a[n_]:=(For[m=1, n*PrimePi[m]!=EulerPhi[m], m++ ];m)
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EXAMPLE
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a(18)=189963073 because 18*pi(189963073)=phi(189963073) and for m<189963073 18*pi(m)!= phi(m).
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MATHEMATICA
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a[n_]:=(For[m=1, n*PrimePi[m]!=EulerPhi[m], m++ ]; m); Do[Print[a[n]], {n, 18}]
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CROSSREFS
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KEYWORD
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more,nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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