function onOpen() {
var colA1Nota = 'A';
var as = SpreadsheetApp.getActiveSheet();
var index = [].concat.apply(
[],
as.getRange([colA1Nota, colA1Nota].join(':')).getDisplayValues()
);
var i = index.length;
while (--i) if (index[i] !== '') break;
as.getRange([colA1Nota, i + 1].join('')).activate();
}