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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 n-tuple of nonnegative integers (b_1, ..., b_n) - namely (1, ..., 1) - such that the sum of the b_i's equals n and the sum of the b_i*k_i's equals the sum of the k_i's.
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0
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OFFSET
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1,2
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COMMENTS
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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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LINKS
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Table of n, a(n) for n=1..7.
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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 another 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 each one once.
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CROSSREFS
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Sequence in context: A018085 A167751 A190822 * A155099 A136322 A160113
Adjacent sequences: A107946 A107947 A107948 * A107950 A107951 A107952
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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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STATUS
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approved
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