The formula for calculating expected losing sequences is as follows:

1 divided by (Losing Strike Rate divided by 100) to the power of 'number of run of outs'.

Important note: The Losing Strike Rate is 100 minus the Win Strike Rate.

Here is an example for a system with a winning Strike Rate of 28% to see how often you should experience a sequence of, say, 14 losers in a row:

=1/(78/100)^14
=1/.78^14
=99.35
=99 (rounded)

The "conclusion" is therefore that every 99 bets you may expect to see 14 losers in a row.