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 A075180 Denominators from e.g.f. 1/(1-exp(-x)) - 1/x. 8
 2, 12, 1, 120, 1, 252, 1, 240, 1, 132, 1, 32760, 1, 12, 1, 8160, 1, 14364, 1, 6600, 1, 276, 1, 65520, 1, 12, 1, 3480, 1, 85932, 1, 16320, 1, 12, 1, 69090840, 1, 12, 1, 541200, 1, 75852, 1, 2760, 1, 564, 1, 2227680, 1, 132, 1, 6360, 1, 43092, 1, 6960, 1, 708, 1, 3407203800, 1, 12, 1, 32640, 1, 388332, 1, 120, 1, 9372, 1, 10087262640, 1, 12 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 COMMENTS Denominators of -zeta(-n), n >= 0, where zeta is Riemann's zeta function. Numerators are +1, A060054(n+1), n >= 1. REFERENCES M. Abramowitz and I. A. Stegun, eds., Handbook of Mathematical Functions, National Bureau of Standards Applied Math. Series 55, Tenth Printing, 1972, p. 807, combined eqs. 23.2.11,14 and 15. LINKS Antti Karttunen, Table of n, a(n) for n = 0..16384 M. Abramowitz and I. A. Stegun, eds., Handbook of Mathematical Functions, National Bureau of Standards, Applied Math. Series 55, Tenth Printing, 1972 [alternative scanned copy]. M. Abramowitz and I. A. Stegun, eds., Handbook of Mathematical Functions, National Bureau of Standards Applied Math. Series 55, Tenth Printing, 1972, p. 807, combined eqs. 23.2.11,14 and 15. FORMULA a(n) = denominator(-Zeta(-n)) = denominator(((-1)^(n+1))*B(n+1)/(n+1)), n >= 0, with Riemann's zeta function and the Bernoulli numbers B(n). a(n) = denominators from e.g.f. (B(-x) - 1)/x, with B(x) = x/(exp(x) - 1), e.g.f. for Bernoulli numbers A027641(n)/A027642(n), n >= 0. From Jianing Song, Apr 05 2021: (Start) a(2n-1) = A006863(n)/2 for n > 0. By the comments in A006863, A006863(n) = A079612(2n) for n > 0. Hence a(n) = A079612(n+1)/2 all odd n. For all even n > 0, we have a(n) = 1, which is also equal to A079612(n+1)/2. For odd n, a(n) is the product of p^(e+1) where p^e*(p-1) divides n+1 but p^(e+1)*(p-1) does not. For example, a(11) = 2^3 * 3^2 * 5^1 * 7^1 * 13^1 = 32760. a(2n-1) = A002445(n)*(2n)/A300711(n), n > 0. (End) a(2*n-1) = A006953(n) for n >= 1. - Georg Fischer, Dec 01 2022 EXAMPLE 1/2, 1/12, 0, -1/120, 0, 1/252, 0, -1/240, 0, 1/132, 0, -691/32760, ... MAPLE a := n -> denom(bernoulli(n+1, 1)/(n+1)); # Peter Luschny, Apr 22 2009 MATHEMATICA a[m_] := Sum[(-2)^(-k-1) k! StirlingS2[m, k], k, 0, m}]/(2^(m+1)-1); Table[Denominator[a[i]], {i, 0, 20}] (* Peter Luschny, Apr 29 2009 *) Table[Denominator[Zeta[-n]], {n, 0, 49}] (* Alonso del Arte, Jan 13 2012 *) CoefficientList[ Series[ EulerGamma - HarmonicNumber[n] + Log[n], {n, Infinity, 48}], 1/n] // Rest // Denominator (* Jean-François Alcover, Mar 28 2013 *) With[{nn=50}, Denominator[CoefficientList[Series[1/(1-Exp[-x])-1/x, {x, 0, nn}], x] Range[0, nn-1]!]] (* Harvey P. Dale, Apr 13 2016 *) PROG (PARI) x='x+O('x^66); egf = 1/(1-exp(-x)) - 1/x; v=Vec(serlaplace(egf)); vector(#v, n, denominator(v[n])) /* Joerg Arndt, Mar 28 2013 */ (PARI) A075180(n) = denominator(bernfrac(n+1)/(n+1)); \\ Antti Karttunen, Dec 19 2018, after Maple-program. (Haskell) a075180 n = a075180_list !! n a075180_list = map (denominator . sum) \$ zipWith (zipWith (%)) (zipWith (map . (*)) a000142_list a242179_tabf) a106831_tabf -- Reinhard Zumkeller, Jul 04 2014 CROSSREFS Cf. A060054, A006232 with A006233. Cf. A006953, A006863, A079612, A242179, A106831, A000142, A300711. Sequence in context: A107773 A221075 A211798 * A227830 A299521 A167164 Adjacent sequences: A075177 A075178 A075179 * A075181 A075182 A075183 KEYWORD nonn,easy,frac AUTHOR Wolfdieter Lang, Sep 06 2002 EXTENSIONS More terms from Antti Karttunen, Dec 19 2018 STATUS approved

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Last modified February 1 19:57 EST 2023. Contains 359995 sequences. (Running on oeis4.)