Number of obtuse triangles on an n X n grid (or geoboard).

Terms

a(0) =0a(1) =0a(2) =24a(3) =236a(4) =1148a(5) =3932a(6) =10760a(7) =25392a(8) =53576a(9) =103824a(10) =188104a(11) =322852a(12) =529116a(13) =835028a(14) =1275360a(15) =1893496a(16) =2742208a(17) =3886568a(18) =5402448a(19) =7381316a(20) =9928860a(21) =13168484a(22) =17243896a(23) =22319864a(24) =28579720a(25) =36237928a(26) =45532720a(27) =56732668