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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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9
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1, 0, 0, 0, 8743, 71193, 640737, 5906061, 65624979, 590624811, 5498542791, 55995364341, 549871699041, 5582882097891, 55828827410391, 542546715730761, 5469955867029591, 53226216007355979, 532262221390168479
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,5
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COMMENTS
| 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
| Max Alekseyev, PARI/GP scripts for miscellaneous math problems [From Max Alekseyev (maxale(AT)gmail.com), Apr 26 2010]
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EXAMPLE
| 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
| (PARI) { a(n) = invsigma(10^n)[1] } [From Max Alekseyev (maxale(AT)gmail.com), Apr 26 2010]
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CROSSREFS
| Cf. A110076, A110078.
Sequence in context: A115614 A165630 A067867 * A203377 A183361 A205254
Adjacent sequences: A110074 A110075 A110076 * A110078 A110079 A110080
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KEYWORD
| nonn
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AUTHOR
| Farideh Firoozbakht (mymontain(AT)yahoo.com), Aug 01 2005
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EXTENSIONS
| a(10)-a(11) from Donovan Johnson (donovan.johnson(AT)yahoo.com) and Farideh Firoozbakht (mymontain(AT)yahoo.com), Nov 22 2008
a(12) onward from Max Alekseyev (maxale(AT)gmail.com), Apr 26 2010
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