Coefficient of x^n in 1/(n+1) * (1 - 2*x - 2*x^2)^(n+1).

Terms

a(0) =1a(1) =-2a(2) =2a(3) =4a(4) =-24a(5) =48a(6) =24a(7) =-464a(8) =1376a(9) =-704a(10) =-9920a(11) =41600a(12) =-55040a(13) =-201216a(14) =1266048a(15) =-2628864a(16) =-3021312a(17) =37696512a(18) =-108659712a(19) =15857664a(20) =1067003904a(21) =-4155138048a(22) =4378226688a(23) =27416125440a(24) =-149814263808a(25) =273526325248a(26) =569660309504