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A250345
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Numerator of the harmonic mean of the first n heptagonal numbers.
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2
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1, 7, 378, 4284, 294525, 3180870, 59376240, 2510766720, 2824612560, 147507544800, 2109357890640, 43721236278720, 1468304851693680, 105943842376051680, 113511259688626800, 121078677001201920, 5274489866864858640, 161957865323732718240, 3931977063692844326160
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OFFSET
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1,2
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LINKS
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EXAMPLE
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a(3) = 378 because the first 3 heptagonal numbers are [1,7,18], and 3/(1/1+1/7+1/18) = 378/151.
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PROG
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(PARI)
harmonicmean(v) = #v / sum(k=1, #v, 1/v[k])
s=vector(30); for(n=1, #s, s[n]=numerator(harmonicmean(vector(n, k, k*(5*k-3)/2)))); s
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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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