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A107949 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. 0
1, 2, 4, 7, 14, 27, 54 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

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.

LINKS

Table of n, a(n) for n=1..7.

EXAMPLE

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.

CROSSREFS

Sequence in context: A018085 A167751 A190822 * A155099 A136322 A160113

Adjacent sequences:  A107946 A107947 A107948 * A107950 A107951 A107952

KEYWORD

hard,nonn

AUTHOR

Vincent Nesme (vnesme(AT)ens-lyon.fr), May 28 2005

STATUS

approved

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Last modified April 6 15:05 EDT 2020. Contains 333276 sequences. (Running on oeis4.)