Reference each 2nd or 3rd column in an array

Busy tweaking a budget template which has column totals for budget, forecast and actuals. In another sheet I want to pull out only the budgeted totals so instead of referencing each field directly, how can I put it in a formula to reference each 3rd column? Sample attached to help clarify.

Try this ...

=INDEX($A$1:$I$1,COLUMNS($A$1:A1)*2-1)

Thank you very much. Now just to amend you formula to reference each 4th column.