I created a sequence field as a function field to show the number of records in browse starting from '1', regardless the 'id' value of the record.

I used the following code

    def _get_sequence(self, cr, uid, ids, fields, args, context=None):
        res={}
        line_o = self.pool.get('budget.transaction.line')
        for o in self.browse(cr,uid,ids):
            res[o.id] = 1+line_o.search_count(cr,uid,[('id','<',o.id)])
        return res
    _columns = {
...
                                                ondelete='cascade', select=True, required=True),
        'sequence': fields.function(_get_sequence,string='Sequence',type='integer', help="Gives the sequence order when displaying a list of lines."),    

The issue with me now is that I need this numbering to be recalculated if I changed the filter of applied on the browse from the advanced search option. How to achieve this. Any help is appreciated.