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A110077
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a(n) is the smallest number m such that sigma(m)=10^n and if there is no such m, a(n)=0.
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10
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1, 0, 0, 0, 8743, 71193, 640737, 5906061, 65624979, 590624811, 5498542791, 55995364341, 549871699041, 5582882097891, 55828827410391, 542546715730761, 5469955867029591, 53226216007355979, 532262221390168479, 5300249369031696429, 52602977416561263909, 531074469279114815229
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OFFSET
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0,5
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COMMENTS
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A110078(n) gives number of solutions of the equation sigma(x)=10^n.
Conjecture: For n>3 a(n) is positive.
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LINKS
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EXAMPLE
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a(9)=590624811 because sigma(590624811)=sigma(3^3*7*3124999) sigma(3^3)*sigma(7)*sigma(3124999)=40*8*3125000=10^9 and 590624811 is the smallest number m with this property (sigma(m)=10^9).
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PROG
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(PARI) { a(n) = invsigma(10^n)[1] } \\ Max Alekseyev, Apr 26 2010
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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