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A074964
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Numbers n such that Max ( sigma(x*y) : 1<=x<=n, 1<=y<=n ) = sigma(n^2).
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4
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OFFSET
| 1,2
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COMMENTS
| Sequence is probably finite.
The next term in the sequence, if it exists, is larger than 40000. - Stewart Gordon, Sep 27 2011
Conjecture: subsequence of A066522, implying finiteness. [Reinhard Zumkeller, Nov 14 2011]
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FORMULA
| A074963(a(n)) = A065764(a(n)). [Reinhard Zumkeller, Nov 14 2011]
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MAPLE
| 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
| (Haskell)
a074964 n = a074964_list !! (n-1)
a074964_list = filter (\x -> a074963 x == a065764 x) [1..]
-- Reinhard Zumkeller, Nov 14 2011
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CROSSREFS
| Cf. A000203.
Sequence in context: A001461 A173383 A048597 * A017822 A179042 A156082
Adjacent sequences: A074961 A074962 A074963 * A074965 A074966 A074967
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KEYWORD
| more,nonn
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AUTHOR
| Benoit Cloitre (benoit7848c(AT)orange.fr), Oct 05 2002
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