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A354860
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a(n) is the denominator of 1/prime(n) + 2/prime(n-1) + 3/prime(n-2) + ... + (n-1)/3 + n/2.
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2
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2, 3, 30, 35, 2310, 15015, 34034, 4849845, 223092870, 154040315, 200560490130, 742073813481, 101416754509070, 6541380665835015, 55899071144408310, 5431526412865007455, 54936010004406075402, 4511091590746421960895, 2619440517026755685293030, 278970415063349480483707695
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OFFSET
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1,1
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COMMENTS
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Denominator of a second order prime harmonic number.
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LINKS
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FORMULA
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a(n) is the denominator of Sum_{j=1..n} Sum_{i=1..j} 1/prime(i).
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EXAMPLE
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1/2, 4/3, 71/30, 124/35, 11111/2310, 92402/15015, 257189/34034, ...
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MATHEMATICA
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Table[Sum[(n - k + 1)/Prime[k], {k, 1, n}], {n, 1, 20}] // Denominator
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PROG
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(Python)
from fractions import Fraction
from sympy import prime, primerange
def a(n): return sum(Fraction(n-i, p) for i, p in enumerate(primerange(1, prime(n)+1))).denominator
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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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STATUS
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approved
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