(1/4)*number of nonsquare rectangles with corners on an n X n grid of points.

Terms

a(0) =1a(1) =6a(2) =20a(3) =52a(4) =111a(5) =214a(6) =376a(7) =620a(8) =967a(9) =1452a(10) =2096a(11) =2952a(12) =4047a(13) =5422a(14) =7128a(15) =9236a(16) =11773a(17) =14834a(18) =18450a(19) =22704a(20) =27675a(21) =33460a(22) =40090a(23) =47708a(24) =56383a(25) =66214a(26) =77276a(27) =89748a(28) =103647a(29) =119206