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A074964
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Numbers k such that Max ( sigma(x*y) : 1 <= x <= k, 1 <= y <= k ) = sigma(k^2).
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4
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OFFSET
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1,2
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COMMENTS
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Sequence is probably finite.
The next term in the sequence, if it exists, is larger than 40000. - Stewart Gordon, Sep 27 2011
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LINKS
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FORMULA
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MAPLE
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with(numtheory): s := proc(n) option remember: return sigma(n): end: a:= proc(n) option remember: if(n=0)then return 0: fi: return max(a(n-1), seq(s(x*n), x=1..n)): end: for n from 1 to 100 do if(a(n)=s(n^2))then printf("%d, ", n): end: od: # Nathaniel Johnston, Sep 26 2011
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PROG
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(Haskell)
a074964 n = a074964_list !! (n-1)
a074964_list = filter (\x -> a074963 x == a065764 x) [1..]
(PARI) isok(k) = vecmax(setbinop((x, y)->sigma(x*y), [1..k])) == sigma(k^2); \\ Michel Marcus, Feb 03 2022
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CROSSREFS
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KEYWORD
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nonn,more
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AUTHOR
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STATUS
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approved
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