Little challenge for HP-15C experts...

[J-F Garnier]

This challenge is basically for users of the genuine HP-15C, not the clones, but there are some implications to these clones especially the 15c CE that I may discuss later.

Reminder: When a key is pressed on the 15C, the display is blanked until the processing of the key is finished. For long processing (solve, integrate, matrix operations, and of course program runs) the blank display is replaced by the flashing 'running' message.
Example:
2 SIN -> blank display for about one second.
but 100 ENTER 50 Cx,y -> 'running' message for about 10s.

The challenge: find a regular, allowed condition (i.e. an operation with a defined argument) that produces a long blank display.
During that long blank state, the HP-15C looks inoperative: the operation can't be interrupted and the 15C can't be turned off/on.

I found a condition with a blank state of more than 15s .

J-F