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A076485
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Solutions to GCD[sigma[x],phi[x]]>GCD[sigma[core(x)],Phi[core(x)]], i.e. when A009223[x]>A066086 or if A066087[x]>0.
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3
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12, 18, 24, 44, 48, 49, 54, 56, 72, 88, 92, 96, 99, 108, 112, 116, 125, 132, 135, 140, 147, 152, 162, 168, 169, 172, 176, 184, 188, 192, 196, 198, 200, 207, 216, 224, 236, 248, 250, 264, 270, 276, 280, 284, 288, 297, 308, 328, 332, 336, 344, 348, 352, 361
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OFFSET
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1,1
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LINKS
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Table of n, a(n) for n=1..54.
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EXAMPLE
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n=12: sigma[12]=28,phi[12]=4, GCD[28,4]=4 core[12]=6, sigma[6]=12,phi[6]=2, GCD[12,2]=2
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MATHEMATICA
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ffi[x_] := Flatten[FactorInteger[x]] lf[x_] := Length[FactorInteger[x]] ba[x_] := Table[Part[ffi[x], 2*w-1], {w, 1, lf[x]}] cor[x_] := Apply[Times, ba[x]] g1[x_] := GCD[DivisorSigma[1, x], EulerPhi[x]] g2[x_] := GCD[DivisorSigma[1, cor[x]], EulerPhi[cor[x]]] Do[s1=g1[n]; s2=g2[n]; If[Greater[s1, s2], Print[n]], {n, 1, 256}]
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CROSSREFS
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Cf. A066086, A066087, A048250, A023900, A000203, A007947, A000010, A009223.
Sequence in context: A055482 A198470 A224218 * A071354 A006622 A124269
Adjacent sequences: A076482 A076483 A076484 * A076486 A076487 A076488
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KEYWORD
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nonn
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AUTHOR
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Labos E. (labos(AT)ana.sote.hu), Oct 17 2002
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STATUS
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approved
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