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A076486
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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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1
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9, 25, 28, 36, 45, 50, 52, 75, 76, 81, 84, 90, 98, 100, 117, 121, 124, 144, 148, 150, 153, 156, 175, 180, 208, 225, 228, 234, 242, 244, 245, 252, 261, 268, 275, 289, 292, 300, 304, 306, 316, 324, 325, 333, 338, 360, 364, 369, 372, 380, 388, 392, 400, 405, 412
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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EXAMPLE
| n=9: sigma[9]=13,phi[9]=6, GCD[13,6]=1, core[9]=3, sigma[3]=4,phi[3]=2, GCD[4,2]=2
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MATHEMATICA
| 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[s2, s1], Print[n]], {n, 1, 256}]
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CROSSREFS
| Cf. A066086, A066087, A048250, A023900, A000203, A007947, A000010, A009223, A076485.
Sequence in context: A068583 A074852 A020252 * A068529 A096059 A065772
Adjacent sequences: A076483 A076484 A076485 * A076487 A076488 A076489
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KEYWORD
| nonn
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AUTHOR
| Labos E. (labos(AT)ana.sote.hu), Oct 17 2002
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