Number of diagonal rectangles with corners on an n X n grid of points.

Terms

a(0) =0a(1) =0a(2) =1a(3) =8a(4) =30a(5) =88a(6) =199a(7) =408a(8) =748a(9) =1280a(10) =2053a(11) =3168a(12) =4666a(13) =6712a(14) =9363a(15) =12728a(16) =16952a(17) =22256a(18) =28681a(19) =36536a(20) =45870a(21) =56936a(22) =69967a(23) =85264a(24) =102860a(25) =123232a(26) =146557a(27) =173128a(28) =203138a(29) =237192