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 A195466 Denominator of the coefficient of x^(2n) in expansion of 1/x^4 - 1/(3*x^2) - 1/(x^3*arctanh(x)). 3
 45, 945, 14175, 467775, 638512875, 1915538625, 488462349375, 7795859096025, 32157918771103125, 316985199315159375, 3028793579456347828125, 478230565177318078125, 3952575621190533915703125, 28304394023345413370350078125, 7217620475953080409439269921875, 21652861427859241228317809765625 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 COMMENTS Prepending 3 to the data gives the denominators of the odd powers in the expansion of 1/arctan(x). - Peter Luschny, Oct 04 2014 LINKS FORMULA 1/x^4 - 1/(3x^2) - 1/(x^3*arctanh x) = 4/45 + 44*x^2/945 + 428*x^4/14175 + 10196*x^6/467775 + ... MAPLE A195466 := proc(n)         1/x^4 -1/(3*x^2) -1/(x^3*arctanh(x)) ;         coeftayl(%, x=0, 2*n) ;         denom(%) ; end proc seq(A195466(n), n=0..15) ; # Or seq(denom(coeff(series(1/arctan(x), x, 2*n+2), x, 2*n+1)), n=1..16); # Peter Luschny, Oct 04 2014 MATHEMATICA a[n_] := Sum[(2^(j+1)*Binomial[2*n+3, j]*Sum[(k!*StirlingS1[j+k, j]*StirlingS2[j+1, k])/(j+k)!, {k, 0, j+1}])/(j+1), {j, 0, 2*n+3}]/(2*n+3); Table[a[n] // Denominator, {n, 0, 15}] (* Jean-François Alcover, Jul 03 2013, after Vladimir Kruchinin's formula in A216272 *) CROSSREFS Cf. A187870 (numerator). Sequence in context: A078761 A034967 A199352 * A010961 A271795 A161690 Adjacent sequences:  A195463 A195464 A195465 * A195467 A195468 A195469 KEYWORD nonn,frac AUTHOR R. J. Mathar, Sep 21 2011 STATUS approved

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Last modified December 4 08:57 EST 2021. Contains 349484 sequences. (Running on oeis4.)