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Search: id:A107949
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| A107949 |
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Smallest k_n such that there exist positive integers 0<k_1<...<k_n such that there exists only one tuple of nonnegative integers (l_1,...,l_n) - namely (1,...,1) - such that the sum of the l_i's equals n and the sum of the l_i.k_i's equals the sum of the k_i's. |
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1
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OFFSET
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1,2
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COMMENT
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These are instances that show that the sequence is at most what is given : 1 1+2 1+2+4 1+2+5+7 1+2+6+12+14 1+3+11+22+23+27 1+2+6+22+44+46+54
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EXAMPLE
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a(3)=4 because 1+2+3=2+2+2 but you can't write 1+2+4 as the sum of three numbers in {1,2,4} in an other way.
a(4)=7 because, for instance, 2+4+5+6=2+5+5+5 but I'll let you check that you can't write 1+2+5+7 as the sum of four numbers in {1,2,5,7}, unless of course you take once each of them.
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CROSSREFS
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Adjacent sequences: A107946 A107947 A107948 this_sequence A107950 A107951 A107952
Sequence in context: A001631 A108758 A018085 this_sequence A136322 A094057 A119267
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KEYWORD
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hard,nonn
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AUTHOR
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Vincent Nesme (vnesme(AT)ens-lyon.fr), May 28 2005
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