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A120285
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Numerator of harmonic number H(p-1) = Sum_{k=1..p-1} 1/k for prime p.
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2
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1, 3, 25, 49, 7381, 86021, 2436559, 14274301, 19093197, 315404588903, 9304682830147, 54801925434709, 2078178381193813, 12309312989335019, 5943339269060627227, 14063600165435720745359, 254381445831833111660789
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OFFSET
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1,2
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COMMENTS
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Prime(n)^2 divides a(n) for n>2.
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LINKS
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FORMULA
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a(n) = numerator(Sum_{k=1..prime(n)-1} 1/k).
a(n) = A061002(n)*prime(n)^2 for n > 2.
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MAPLE
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f3:=proc(n) local p;
p:=ithprime(n);
numer(add(1/i, i=1..p-1));
end proc;
[seq(f3(n), n=1..20)];
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MATHEMATICA
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Numerator[Table[Sum[1/k, {k, 1, Prime[n]-1}], {n, 1, 20}]]
Table[HarmonicNumber[p], {p, Prime[Range[20]]-1}]//Numerator (* Harvey P. Dale, May 18 2023 *)
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PROG
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(PARI) a(n) = my(p=prime(n)); numerator(sum(k=1, p-1, 1/k)); \\ Michel Marcus, Dec 25 2018
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CROSSREFS
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KEYWORD
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frac,nonn
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AUTHOR
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STATUS
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approved
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