For example, say a party of adventurers is journeying through a wilderness region which is known to be patrolled by Orcs and other nasties.
A party of 2-3 adventurers would surely attract less attention than ten. Think Sam and Frodo vs. the entire Fellowship. On the other hand, monsters might steer clear of an armed party of 500 (the PCs + lots of retainers) no matter how much noise they make as they march.
I think OP is trying to account more for the fact that a larger group of adventurers reasonably will attract more attention than a smaller group. This isn't a tailoring of difficulty per se, but more of an expression of the amount of "noise" the adventurers make going through hostile territory.
In this case I would advocate rolling multiple times on the encounter table. A nonlinear buildup would probably be accurate, so let's say we roll a number of times equal to the square root of the size of the party, which is more or less the party's cross-section if you imagine them as a vaguely circular blob moving through the region.
This means that a party of 2-3 adventurers gets encounters about as often as the rules suggest. A party of 4-8 adventurers gets encounters roughly twice as often and sometimes they run into twice as many bad guys.
No. I notice you didn't specify edition, but I'm familiar with them all—and none that use random encounters (and tables thereof) tailor their numbers to the size of the party. The editions that include that specific kind of randomness are already aiming to provide a naturalistic experience, where the world is not tailored to the party, and having random encounter tables is one way they achieve that. Tailoring the number of monsters encountered would be a small contradiction of the reason these editions include random encounters in the first place.
However, there is a "native" way of tailoring random encounters to the party in these games. First, the players are informed that it's up to them to engage with encounters or not (assuming they're not surprised), and that exploring into more dangerous areas is a choice on their part that will bring greater dangers (possibly surprising them).
Second, the DM has the option of backing this up with customised tables for certain areas of the wilderness. By choosing what is on your tables, you are effectively tailoring the encounters to a theoretical group of X ability. By placing these tables around your world, you are saying "This place is dangerous to parties below X ability". The players then explore—and their observations, and choices about whether to continue or leave for "greener" exploration pastures, is how the game adjusts difficulty to the party.
(As for the issue of attracting less attention, that is usually handled by modifiers to the surprise roll, or outright just deciding that one side is aware of the encounter before the other side is. Hence, an army of orcs is still less likely to notice a couple of hobbits, but not likely to be somehow a smaller group of orcs just because it's two hobbits and not ten.)
So to sum: No edition of D&D that uses random tables concerns itself about that kind of tailoring difficulty to the party, because it is already assuming that it's the players' responsibility to tailor difficulty using their ability to choose where they go, and what enemies to engage with there. Therefore, if you're looking for tables to use in any edition that have their numbers pegged to the party's size, you won't find any that are pre-made.
