Central binomial coefficients: binomial(2*n,n) = (2*n)!/(n!)^2.

Terms

a(0) =1a(1) =2a(2) =6a(3) =20a(4) =70a(5) =252a(6) =924a(7) =3432a(8) =12870a(9) =48620a(10) =184756a(11) =705432a(12) =2704156a(13) =10400600a(14) =40116600a(15) =155117520a(16) =601080390a(17) =2333606220a(18) =9075135300a(19) =35345263800a(20) =137846528820a(21) =538257874440