Try to enter the Google account once you input wrong patterns. The tablet should be connected to Data or WiFi. Once you're prompted to enter the account, do it and wait for its reply. If it's says it's not available, then you need to hard reset the tablet.
Hard reset instructions:
- Turn off the tablet
- Press Volume Up + Power + Home
- When Samsung logo appears, release Power
- Use Volume buttons and select Wipe Data/Factory reset
- Confirm selection with Power
Some data will be lost, you will gain access to the tablet.