Investec has again reiterated its buy recommendation for UK lender Barclays, telling investors to 'do the maths' as the stock is still cheap."Although Barclays enjoyed an 8% two-day bounce prior to Friday's broad sell-off, we continue to believe that the current entry level offers value ahead of the Q1 IMS on April 26th," the broker said.Investec upgraded its rating on the stock on Wednesday last week saying that the recent underperformance in the shares offered a "clear opportunity" to buy into the stock.Despite the broker admitting that it still retains a "sceptical" medium-term outlook - it expects a 2013 return on equity of just 7.6% compared to the group's 13% target - it says that it remains a buyer ahead of the first quarter update later this month.BC