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Search: id:A112421
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| A112421 |
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Number of 6 element subsets of {1,2,3,...,n} for which the sum-set has 12 elements. |
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+0
1
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| 2, 4, 6, 8, 10, 12, 16, 20, 24, 28, 32, 36, 42, 48, 54, 60, 66
(list; graph; listen)
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OFFSET
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7,1
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FORMULA
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2x^7/((1-x)^2 (1-x^6)
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EXAMPLE
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a(7)=2 because the two sets {1 2 3 4 5 7} and (1 3 4 5 6 7} have sum-sets
{2 3 4 5 6 7 8 9 10 11 12 14} and {2 4 5 6 7 8 9 10 11 12 13 14}, respectively and each of these sum-sets has 12 elements.
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CROSSREFS
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Sequence in context: A114270 A085154 A109884 this_sequence A022483 A100180 A101814
Adjacent sequences: A112418 A112419 A112420 this_sequence A112422 A112423 A112424
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KEYWORD
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nonn
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AUTHOR
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David S Newman (DavidSNewman(AT)hotmail.com), Dec 10 2005
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