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A250344
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Numerator of the harmonic mean of the first n hexagonal numbers.
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1
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1, 12, 90, 1680, 6300, 83160, 1261260, 576576, 11027016, 1163962800, 1280359080, 32125373280, 174012438600, 80313433200, 2495453103000, 165032631878400, 175347171370800, 1299631976042400, 50757848842100400, 53429314570632000, 2300131992265707600
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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) = 90 because the first 3 hexagonal numbers are [1,6,15], and 3/(1/1+1/6+1/15) = 90/37.
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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*(2*k-1))))); 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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