Largest square <= binomial(2n,n).

Terms

a(0) =1a(1) =1a(2) =4a(3) =16a(4) =64a(5) =225a(6) =900a(7) =3364a(8) =12769a(9) =48400a(10) =184041a(11) =703921a(12) =2702736a(13) =10394176a(14) =40106889a(15) =155102116a(16) =601034256a(17) =2333566249a(18) =9075039169a(19) =35345128009a(20) =137845868176a(21) =538256995600