Reduce[a^2+b^2==c^2&&0<a<100&&0<b<100&&0<c<100,{a,b,c},Integers]

ListPlot3D[{a,b,c}/.Solve[a^2+b^2==c^2&&0<a<100&&0<b<100&&0<c<100,{a,b,c},Integers],InterpolationOrder->0,Mesh->None,ColorFunction->"Rainbow",Filling->Bottom,BoxRatios->1]