Small issue function offset

Breaking down your formula you want
=IFERROR(C5=OFFSET(C5,0,-1)+1,0)
to be true OR you want
=C5=D5-1 to be true not both. Only one has to be true for "C5" to trigger.
Other wise it will put "-"

if you want BOTH conditions to be bet to place "C5" you need to use AND.

However it appears you want Both conditions to be met for K5, but then go back to "OR" and trigger when only one of the conditions are met
That's incredibly confusing because it sounds like you want a formula to look back on itself to make sure it is still "incrementally increasing"
That is circular reasoning.

Since the number before 1 is 0, it is counting 1 as "TRUE".
Put in any other number in that field and it will not show up. It will put the "-" because neither conditions are met.
Your formula works as intended, UNLESS you just really hate the number 1 in which case you can make a nested IF statement saying

=IF(C5=1,"Screw You, I hate number 1",IF(OR(IFERROR(C5=OFFSET(C5,0,-1)+1,0),C5=D5-1),C5,"-"))

sorry Glenn Kennedy, I didn't explain it right

The number 1 must appear if the next number is the number 2.

So if I type:

1, 2, 100, 140, 145, 146, 200

The numbers that should appear are (all sequences):

1, 2, 145, 146

With the previous formulas, the number 1 appears in anyway, being a sequence or not. I'm trying to get all the numbers in sequence

If I type

1, 200, 205, 210, 300, 301

The numbers that should appear are (all sequences):
300, 301

in this case, the number 1 will not appear because the next number is the number 200

Attachment 817190

hello thenewkidd,

thanks for answer. I dont hate number 1 kkkkkkkkkk

the number should appear if the next number is 2. If you open the sample you will see that it is working good, but when you type the number 1, the number 1 will always appear

hi Glenn Kennedy.

It is perfect

thanks a lot

Have a great weekend