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Search: id:A077103
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| A077103 |
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Numbers n such that GCD[a,b] is not equal to GCD[a+b,a-b], where a=sigma[n]=A000203(n) and b=phi[n]=A000010(n). |
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| 1, 2, 12, 15, 30, 39, 44, 55, 56, 76, 78, 87, 95, 99, 110, 111, 125, 140, 143, 147, 159, 171, 172, 174, 175, 183, 184, 190, 198, 215, 216, 222, 236, 247, 250, 252, 264, 268, 286, 287, 294, 295, 303, 315, 318, 319, 327, 332, 335, 336, 342, 350, 357, 363, 364
(list; graph; listen)
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OFFSET
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1,2
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FORMULA
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GCD[A000010(n), A000203(n)] not equal to GCD[A065387(n), A051612(n)]; or A055008(n) is not equal A077099(n)
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EXAMPLE
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n=76: a=sigma[76]=140,b=phi[76]=36,a+b=176,a-b=104, GCD[a,b]=GCD[140,36]=4<GCD[a+b,a-b]=GCD[176,104]=8.
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MATHEMATICA
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Do[s=GCD[a=DivisorSigma[1, n], b=EulerPhi[n]]; s1=GCD[a+b, a-b]; If[ !Equal[s, s1], Print[{n, a, b, a+b, a-b, s, s1, s1/s}]], {n, 1, 1000}]
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CROSSREFS
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Cf. A000010, A000203, A051612, A065387, A055008, A077099.
Sequence in context: A076484 A108969 A118516 this_sequence A036499 A107607 A102975
Adjacent sequences: A077100 A077101 A077102 this_sequence A077104 A077105 A077106
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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), Nov 12 2002
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