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Search: id:A073110
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| A073110 |
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Number of permutations p of (1,2,3,...,n) such that sigma(1+p(1))+sigma(2+p(2))+...+sigma(n+p(n))=2*n^2. |
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+0
1
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| 0, 1, 0, 2, 10, 37, 121, 725, 5160, 31794, 279136
(list; graph; listen)
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OFFSET
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1,4
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COMMENT
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It seems that for any permutation p of (1,2,3,...,n) for n>3, the equation: sigma(1+p(1))+sigma(2+p(2))+...+sigma(n+p(n))=m*n^2 has solutions for m=2 only.
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PROGRAM
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(PARI) a(n)=sum(k=1, n!, if(sum(i=1, n, sigma(i+component(numtoperm(n, k), i)))-2*n^2, 0, 1))
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CROSSREFS
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Sequence in context: A100535 A001582 A026546 this_sequence A034547 A124646 A124635
Adjacent sequences: A073107 A073108 A073109 this_sequence A073111 A073112 A073113
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KEYWORD
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nonn
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AUTHOR
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Benoit Cloitre (benoit7848c(AT)orange.fr), Aug 19 2002
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EXTENSIONS
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2 more terms from Ryan Propper (rpropper(AT)stanford.edu), Aug 27 2005
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