For 1,2,3,4,5,6 to come up the first number can be any of 43 ie 43/49 then the next must be one of 5 specific numbers 5/48 then 4/47 then 3/46 then 2/45 then 1/44.
Which I make 1.9 million to 1
There are 43 possible sequences of consecutive numbers so roughly half a million to 1 against one of them coming up.
(some complexities around the end numbers but this is very rough)
So probability of not sequential is half a million to one on.
but the odds of a particular sequential set are the same as those of a randomly chosen set
But you said random that's difficult because you have to define what's random
There's 2,4,6,8,10,12 that could come up or 29, 31, 37, 41, 43, 47 (primes) or 3,4,7,11,18,29 a fibonacci sequence.
So calculating the odds of a consecutive sequence coming up is one thing and the odds are long, calculating the odds of the sequence being random and not displaying a pattern is different and I have no idea how you'd even start that.