URxvt.keysym.Control-Up: \033[1;5A URxvt.keysym.Control-Down: \033[1;5B
URxvt.keysym.Control-Left: \033[1;5D URxvt.keysym.Control-Right: \033[1;5C
Probably to behave more like XTerm and fix a few other issues I had with other programs. But, it turns out, tcell expects the original sequence: https://github.com/gdamore/tcell/blob/main/terminfo/r/rxvt/term.go#L487
Hmm.~