for number-to-register and increment-register.
(define-key ctl-x-map "ri" 'insert-register)
(define-key ctl-x-map "rg" 'insert-register)
(define-key ctl-x-map "rr" 'copy-rectangle-to-register)
+(define-key ctl-x-map "rn" 'number-to-register)
+(define-key ctl-x-map "r+" 'increment-register)
(define-key ctl-x-map "rc" 'clear-rectangle)
(define-key ctl-x-map "rk" 'kill-rectangle)
(define-key ctl-x-map "rd" 'delete-rectangle)