Dynamo 2.0 Point.ByCoordinates Warning: The Point.ByCoordinates operation failed. The type initializer for 'Autodesk.LibG.LibGPINVOKE' threw an exception

Lists start at index 0
Try the following

a[0];
a[1];
a[2];

If you are using a hosted version of Dynamo, make sure that your Revit / Civil 3D / whatever you are launching Dynamo from is fully updated.

If you are using Dynamo Sandbox, make sure Revit/AutoCAD/ another Autodesk product is installed.