Coefficients of Legendre polynomials.

Terms

a(0) =3a(1) =15a(2) =105a(3) =315a(4) =6930a(5) =18018a(6) =90090a(7) =218790a(8) =2078505a(9) =4849845a(10) =22309287a(11) =50702925a(12) =1825305300a(13) =4071834900a(14) =18032411700a(15) =39671305740a(16) =347123925225a(17) =755505013725