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E.g.f.: (x^2/2-2*x+3)*tan(x/2+Pi/4)-3*x^3-x-3.
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%I #8 Mar 12 2019 09:21:02

%S 0,0,0,-15,5,18,66,298,1511,8670,55168,386394,2951673,24428654,

%T 217723390,2079109386,21177620171,229195610430,2626388037372,

%U 31768201320634,404485298533085,5407570127090958,75736453324821754,1108952444876609898,16943545270848408495

%N E.g.f.: (x^2/2-2*x+3)*tan(x/2+Pi/4)-3*x^3-x-3.

%H Y. Sano, <a href="https://doi.org/10.1016/j.disc.2006.11.019">The principal numbers of K. Saito for the types A_l, D_l and E_l</a>, Discr. Math., 307 (2007), 2636-2642.

%F a(n) ~ n! * 2^(n-1) * (24 + (Pi-8)*Pi) / Pi^(n+1). - _Vaclav Kotesovec_, Mar 12 2019

%Y Cf. A131656.

%K sign

%O 0,4

%A _N. J. A. Sloane_, Oct 30 2007