"4mula freak" wrote...
....
I know how to name lists or cells, so I think seq: is just one cell, with
the formula you gave. . . .

No, seq is a defined name. Run the menu command Insert Name Define,
enter seq as the name, and enter the formula I gave previously in the Refers
to field.

. . . No variable in seq's formula, right? . . .

Correct.

. . . Why 1024? . . .

Just a biggish number. You could make it larger to handle longer strings,
but it's also a trade-off with performance - you don't what to do to much
unnecessary processing.

. . . Which way using LOOKUP here - Vector or Array? . . .

Vector. Count the arguments.

. . . We're seeking a Boolean true/false value here (0, or 1), right?. . .

Not quite. The 2nd argument is 1/(boolean expression), so the denominator is
converted to 1 for TRUE, 0 for FALSE, so the 2nd argument evaluates to 1 for
TRUE and #DIV/0! for FALSE. The largest value in the 2nd argument array is
1, and the 1st argument lookup value is 2. When given a lookup value greater
than any value in its 2nd argument, LOOKUP will always match the *last*
value less than the lookup value.