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Search: id:A055940
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| A055940 |
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Counterbalanced numbers: Composite n such that Phi[n]/(DivisorSigma[1,n]-n) is an integer. |
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+0
5
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| 133, 403, 583, 713, 817, 2077, 2623, 2923, 4453, 4717, 5311, 5773, 7093, 7747, 9313, 11023, 11581, 11653, 12877, 14353, 15553, 19303, 20803, 21409, 21733, 21971, 24307, 31169, 35033, 39283, 39337, 43873, 46297, 46357, 50573, 50879, 53863
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OFFSET
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1,1
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COMMENT
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q=A000010(n)/A001065(n) is integer and n is composite.
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EXAMPLE
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n=133=7.19: Phi[133]=108, Sigma[133]-133=1+7+19=27, q=4
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MATHEMATICA
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Do[s=EulerPhi[n]/(DivisorSigma[1, n]-n); If[ !PrimeQ[n]&&IntegerQ[s], Print[n]], {n, 2, 1000000}]
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CROSSREFS
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Cf. A000010, A001065, A068418, A020492, A070037.
Sequence in context: A115518 A064903 A070158 this_sequence A137879 A020237 A117565
Adjacent sequences: A055937 A055938 A055939 this_sequence A055941 A055942 A055943
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KEYWORD
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easy,nonn
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AUTHOR
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Robert G. Wilson v (rgwv(AT)rgwv.com), Jul 22 2000
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