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OFFSET
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1,1
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COMMENT
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No other terms below 10^10.
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EXAMPLE
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phi(sigma(20575296))=phi(71238999)=41150592=2*20575296, so 20575296 is in the sequence.
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MATHEMATICA
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Do[If[EulerPhi[DivisorSigma[1, n]]==2n, Print[n]], {n, 350000000}]
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CROSSREFS
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Cf. A071525, A135238, A135239.
Sequence in context: A071226 A134369 A151654 this_sequence A058432 A058458 A077575
Adjacent sequences: A135237 A135238 A135239 this_sequence A135241 A135242 A135243
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KEYWORD
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bref,more,nonn
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AUTHOR
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Farideh Firoozbakht (mymontain(AT)yahoo.com), Dec 26 2007
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EXTENSIONS
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Search extended to 10^10 by Max Alekseyev (maxale(AT)gmail.com), Sep 25 2009
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