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Search: id:A110590
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| A110590 |
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Balanced numbers n (A020492) such that phi(n) is not divisible by 12. |
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+0
2
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OFFSET
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1,2
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COMMENT
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The only balanced numbers such that sigma(n) is not divisible by 12 are 1, 2, 3.
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FORMULA
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sigma(n)/phi(n) is an integer and phi(n) mod 12 > 0.
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MAPLE
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with(numtheory): BNM:=[]: for z from 1 to 1 do for n from 1 to 100000 do if phi(n) mod 12 > 0 and sigma(n) mod phi(n) = 0 then BNM:=[op(BNM), n] fi; od; od; BNM; # after 3828 there no others out to 2*10^6.
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MATHEMATICA
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fQ[n_] := Block[{ds = DivisorSigma[1, n], ep = EulerPhi@n}, Mod[ep, 12] > 0 && IntegerQ[ds/ep]]; Do[ If[ fQ@n, Print@n], {n, 4*10^8}] (from Robert G. Wilson v (rgwv(at)rgwv.com), Jun 19 2006)
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CROSSREFS
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Cf. A000010, A000203, A020492.
Sequence in context: A015765 A015771 A020492 this_sequence A111271 A070926 A124485
Adjacent sequences: A110587 A110588 A110589 this_sequence A110591 A110592 A110593
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KEYWORD
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nonn
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AUTHOR
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Walter A. Kehowski (wkehowski(AT)cox.net), Sep 13 2005
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