Comment 18 for bug 96676

Another file that supports my understanding: debian's (and therefore presumably Ubuntu's) own xterm terminfo file from ncurses-base, includes the comment:

# Function keys with modifiers (Sun/PC):
# -------------------------------------
# Shift-Fx - kf{12+x}
# Control-Fx - kf{24+x}
# Shift-Control-Fx - kf{36+x}