Find the biggest gap between numbers in rows

Try this...

Data Range

	A	B	C
1			Find
2	2,3,4,6,7,8,12,13,14,24,30,42,45,46,48,50,56,58,59,61		59
3	1,2,6,8,11,12,13,16,17,21,24,27,28,33,34,42,44,48,58,61		4
4	3,7,10,13,14,15,18,21,23,24,25,29,30,34,37,48,51,56,57,60	------	------
5	8,11,13,16,17,19,21,27,29,35,36,39,42,44,46,50,53,54,57,60
6	2,4,7,9,21,26,28,30,32,34,35,37,38,39,43,44,50,60,61,62
7	10,13,15,18,21,22,23,24,25,26,40,42,48,49,51,52,56,59,61,62
8	1,2,4,7,14,15,18,20,24,29,30,32,35,41,42,50,52,55,58,62
9	1,4,8,9,10,12,17,24,25,33,37,41,43,44,46,49,52,59,61,62
10	1,2,4,6,9,12,15,17,21,24,30,31,32,36,41,44,47,48,51,58
11	2,7,10,12,15,16,20,24,25,27,30,33,39,44,45,52,54,55,58,60
12	5,7,10,11,20,22,24,31,32,33,36,38,39,41,43,47,50,52,56,58
13	3,6,8,9,14,15,19,21,25,28,34,37,39,45,47,54,55,56,57,59
14	1,2,3,4,5,8,14,15,18,20,23,31,33,37,42,45,46,51,52,55

This array formula** entered in C3:

=MAX(FREQUENCY(IF(ISERROR(FIND(","&C2&",",","&A2:A14&",")),ROW(A2:A14)),IF(ISNUMBER(FIND(","&C2&",",","&A2:A14&",")),ROW(A2:A14))))

** array formulas need to be entered using the key
combination of CTRL,SHIFT,ENTER (not just ENTER).
Hold down both the CTRL key and the SHIFT key
then hit ENTER.

This may be a bit slow to calculate on >12500 rows of data.

Also, you may have to replace the commas in the formula with semi-colons depending on your regional settings.