E.g.f. (2-2x-x^2)/((1-2x)(1-x^2)).

A052647

E.g.f. (2-2x-x^2)/((1-2x)(1-x^2)).

Terms

    a(0) =2a(1) =2a(2) =10a(3) =48a(4) =408a(5) =3840a(6) =46800a(7) =645120a(8) =10362240a(9) =185794560a(10) =3719520000a(11) =81749606400

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