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A124235
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a(n) = numerator of (Sum_{k=1..n} H(2k)(2k)!/(k!(k+n+1)!) = Sum_{k=0..n-1} H(n-k)(2k)!/ (k!(k+n+1)!)), where H(k) = Sum_{j=1..k} 1/j (i.e., the k-th harmonic number).
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2
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1, 1, 17, 877, 26, 6827, 12310607, 105059, 604489, 49568347, 12933671, 143562866581, 2406858923083, 35714915113, 530084035699, 7390807289267, 1031992153425439, 225749374968517, 8052704479475951909
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OFFSET
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1,3
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LINKS
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MATHEMATICA
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f[n_] := Numerator[Sum[HarmonicNumber[2k]*Factorial[2k]/(Factorial[k]*Factorial[k + n + 1]), {k, n}]]; Table[f[n], {n, 21}] (* Ray Chandler, Oct 23 2006 *)
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PROG
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(PARI) H(n)={ if(n==0, 0, sum(k=1, n, 1/k)) ; }
A124235(n)={ numerator(sum(k=1, n, H(2*k)*(2*k)!/k!/(k+n+1)!)) ; }
A124235alt(n)={ numerator(sum(k=0, n-1, H(n-k)*(2*k)!/k!/(k+n+1)!)) ; } \\ R. J. Mathar, Oct 23 2006
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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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EXTENSIONS
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STATUS
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approved
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