My flatmate always forgets his key, so now we have installed a small locker outside the room where a spare is located. So that my flatmates doesn't forget the code we made this small riddle for him, if he can find the pattern he finds the missing number. The missing number is also the code for unlocking the locker. Please help him, he forgot his key (and the pattern) again....
The pattern starts at the top left corner.
If you sum first one number, secondly three numbers, thridly five numbers and lastly seven numbers the pattern should be clear!