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A090302
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Begin with n and consider numbers obtained by successively subtracting 0, 1, 2, 3, ...; a(n) = largest prime that arises in the process, i.e., largest prime of the form n - T(r), where T(r) is the r-th triangular number; or 0 if no such number exists.
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2
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0, 2, 3, 3, 5, 5, 7, 7, 3, 7, 11, 11, 13, 13, 5, 13, 17, 17, 19, 19, 11, 19, 23, 23, 19, 23, 17, 13, 29, 29, 31, 31, 23, 31, 29, 0, 37, 37, 29, 37, 41, 41, 43, 43, 17, 43, 47, 47, 43, 47, 41, 37, 53, 53, 19, 53, 47, 43, 59, 59, 61, 61, 53, 61, 59, 11, 67, 67, 59, 67, 71
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OFFSET
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1,2
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COMMENTS
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a(p) = p if p is a prime.
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LINKS
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FORMULA
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Largest prime of the form n - r(r+1)/2.
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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