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%I #9 Mar 26 2021 19:28:02
%S 1,40,2464,229760,30633856,5561407488,1322489954304,399463775797248,
%T 149519094622027776,67960463478175825920,36884466463352967659520,
%U 23566236397584291201024000,17511732541318788803985408000
%N Scaled coefficients of (arctanh x)^4.
%F E.g.f.: (arctanh x)^4 or (1-x^2)^-1 * (arctanh x)^3.
%F a(n) is coefficient of x^(2*n+4) in (arctanh x)^4, multiplied by (2*n+4)!/4!.
%e (arctanh x)^4 = x^4 + 4/3*x^6 + 22/15*x^8 + 1436/945*x^10 + ...
%t a[n_] := SeriesCoefficient[ArcTanh[x]^4, {x, 0, 2n+4}]*(2n+4)!/4!;
%t a /@ Range[0, 12] (* _Jean-François Alcover_, Mar 26 2021 *)
%Y Cf. A049214, A049216, A049217.
%K nonn
%O 0,2
%A Joe Keane (jgk(AT)jgk.org)
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