Number of convex quadrilaterals on an n X n grid (or geoboard).

Terms

a(0) =0a(1) =1a(2) =70a(3) =1038a(4) =7398a(5) =35727a(6) =130768a(7) =400116a(8) =1062016a(9) =2531001a(10) =5529310a(11) =11272710a(12) =21639022a(13) =39559591a(14) =69283632a(15) =116910052a(16) =190977408a(17) =303286461a(18) =469431366a(19) =710400658a(20) =1053055398a(21) =1532253131a(22) =2192246528a(23) =3088876728a(24) =4290532688a(25) =5882825641a(26) =7969711934a(27) =10677299074a(28) =14156978846a(29) =18591603883