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A340720
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Least positive number k such that sigma(k) = n * sigma(k+1).
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2
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OFFSET
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1,1
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LINKS
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EXAMPLE
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n | sigma(a(n)) | sigma(a(n)+1)
----+-------------+--------------
1 | 24 | 24
2 | 28 | 14
3 | 546 | 182
4 | 103680000 | 25920000
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PROG
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(PARI) {a(n) = my(k=1); while(sigma(k)!=n*sigma(k+1), k++); k}
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CROSSREFS
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KEYWORD
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nonn,more,hard
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AUTHOR
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STATUS
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approved
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