Number of ways to place 3 nonattacking grasshoppers on a chessboard of size n x n.

Terms

a(0) =0a(1) =4a(2) =76a(3) =516a(4) =2172a(5) =6860a(6) =17904a(7) =40796a(8) =83976a(9) =159732a(10) =285220a(11) =483604a(12) =785316a(13) =1229436a(14) =1865192a(15) =2753580a(16) =3969104a(17) =5601636a(18) =7758396a(19) =10566052a(20) =14172940a(21) =18751404a(22) =24500256a(23) =31647356a(24) =40452312a(25) =51209300a(26) =64250004a(27) =79946676