This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A035047 #22 Jul 08 2025 21:29:49 %S A035047 1,2,3,4,15,12,105,24,315,120,3465,40,45045,280,45045,560,765765,5040, %T A035047 14549535,5040,14549535,55440,334639305,55440,1673196525,720720, %U A035047 5019589575,720720,145568097675,720720 %N A035047 Denominators of alternating sum transform (PSumSIGN) of Harmonic numbers H(n) = A001008/A002805. %H A035047 Robert Israel, <a href="/A035047/b035047.txt">Table of n, a(n) for n = 1..2000</a> %H A035047 N. J. A. Sloane, <a href="/transforms.txt">Transforms</a> %F A035047 G.f. for A035048(n)/A035047(n) : log(1-x)/(x^2-1). - _Benoit Cloitre_, Jun 15 2003 %F A035047 a(n) = denominator((-1)^(n+1)*1/2*(log(2)+(-1)^(n+1)*(gamma+1/2*(psi(1+n/2)-psi(3/2+n/2))+psi(2+n)))), with gamma the Euler-Mascheroni constant. - [_Gerry Martens_, Apr 28 2011] %p A035047 S:= series(log(1-x)/(x^2-1), x, 101): %p A035047 seq(denom(coeff(S,x,j)),j=1..100); # _Robert Israel_, Jun 02 2015 %o A035047 (PARI) a(n)=denominator(polcoeff(log(1-x)/(x^2-1)+O(x^(n+1)),n)) %Y A035047 Cf. A035048. %K A035047 nonn,frac,easy %O A035047 1,2 %A A035047 _N. J. A. Sloane_