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A230035
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Numbers which can be represented as a sum of 3 relatively prime positive integers such that each pair of them is not coprime.
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2
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31, 37, 41, 43, 47, 49, 53, 55, 59, 61, 65, 67, 69, 71, 73, 77, 79, 83, 85, 86, 87, 89, 91, 92, 93, 95, 97, 99, 101, 103, 106, 107, 109, 111, 113, 115, 116, 117, 118, 119, 121, 122, 123, 125, 127, 128, 129, 131, 133, 134, 135, 136, 137, 139, 141, 143
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OFFSET
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1,1
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COMMENTS
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Each number beginning from 2731 is in a(n).
Generally for every positive integer k there is only finite quantity of numbers which can't be represented as a sum of k+1 relatively prime positive integers such that any k of them are not coprime.
For instance, for k = 3 570570 is the largest number which cannot be represented.
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LINKS
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EXAMPLE
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31 is in a(n) because 31 = 6 + 10 + 15 and gcd(6, 10, 15) = 1 however gcd(6, 10) = 2, gcd(6, 15) = 3, gcd(10, 15) = 5.
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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