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A191645
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Numerators of the n-th partial "harmonic" sum of 1 + inverse semiprimes.
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1
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5, 17, 55, 293, 2141, 445, 457, 5153, 131597, 1745411, 1772711, 30586537, 31024117, 597115873, 604577173, 14050770329, 99311504603, 100230122303, 101081931443, 101903852543
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OFFSET
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1,1
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COMMENTS
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Denominators appear to be the same as A140123. The fractions begin: 5/4, 17/12, 55/36, 293/180, 2141/1260, 445/252, 457/252, 5153/2772, 131597/69300, ...
This is the semiprime analog of A024528.
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LINKS
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EXAMPLE
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a(1) = 5 because 1 + 1/4 = 5/4.
a(2) = 17 because 1 + 1/4 + 1/6 = 17/12.
a(3) = 55 because 1 + 1/4 + 1/6 + 1/9 = 55/36.
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MAPLE
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MATHEMATICA
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With[{sp=Join[{1}, Select[Range[100], PrimeOmega[#]==2&]]}, Rest[ Numerator[ Accumulate[1/sp]]]] (* Harvey P. Dale, May 01 2015 *)
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PROG
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(PARI) s=1; for(k=1, 99, bigomega(k)==2 & print1(numerator(s+=1/k)", ")) \\ M. F. Hasler, Jun 17 2011
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CROSSREFS
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KEYWORD
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nonn,easy,frac
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AUTHOR
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STATUS
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approved
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