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A078559
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Numerator of Product_{i=1..n} (p_i+1)/(p_i-1) where p_i is the i-th prime.
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2
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3, 6, 9, 12, 72, 84, 189, 21, 252, 270, 288, 304, 1596, 152, 3648, 49248, 295488, 1526688, 17302464, 622888704, 640191168, 1707176448, 10243058688, 23046882048, 23527025424, 599939148312, 47054050848, 2540918745792
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OFFSET
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1,1
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REFERENCES
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R. K. Guy, Unsolved Problems in Number Theory, B48.
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LINKS
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FORMULA
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MAPLE
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Q:= 1: p:= 1:
for n from 1 to 100 do
p:= nextprime(p);
Q:= Q * (p+1)/(p-1);
A[n]:= numer(Q);
od:
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MATHEMATICA
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Numerator[Table[Product[(Prime[i] + 1)/(Prime[i] - 1), {i, n}], {n, 30}]] (* Alonso del Arte, Aug 23 2011 *)
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PROG
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(PARI) a(n) = numerator(prod(i=1, n, (prime(i)+1)/(prime(i)-1))); \\ Michel Marcus, May 11 2018
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CROSSREFS
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KEYWORD
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nonn,frac
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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