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Search: id:A065149
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| A065149 |
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Phi[m]*Sigma[m] is divisible by m-1. |
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+0
1
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| 10, 33, 65, 136, 145, 261, 385, 451, 897, 946, 1281, 1441, 1665, 1729, 2241, 2353, 3585, 5185, 6721, 7201, 8380, 8911, 8961, 11521, 11782, 12673, 12801, 17101, 18241, 20737, 25201, 26625, 26677, 26937, 29697, 29953, 30721, 30889, 32896
(list; graph; listen)
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OFFSET
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0,1
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FORMULA
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Mod[A000010[m]*A000203[m], m-1]=0, m is composite.
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EXAMPLE
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m=136, Phi[136]=64, Sigma[136]=270, product=17280, quotient=128; for primes the formula holds.
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MATHEMATICA
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Do[s=EulerPhi[n]*DivisorSigma[1, n]; If[IntegerQ[s/(n-1)]&&!PrimeQ[n], Print[n]], {n, 1, 100000}]
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CROSSREFS
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A000010, A000203, A062354, A011257.
Adjacent sequences: A065146 A065147 A065148 this_sequence A065150 A065151 A065152
Sequence in context: A067878 A067877 A063160 this_sequence A085490 A081437 A003012
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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 18 2001
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