I'm sure there's a nice mathematical way of doing this, but since no-one has replied with one yet, here's a brute-force type of way to deal with it.

Do a loop through the pool of numbers, for each of those loop do another loop through the rest of the numbers to find one that is next in sequence (e.g. if number is '4' look for '5'). If it finds one then it loops again looking for the next highest number until it runs out of numbers.

Some csharp/pseudo type code:

int[] pool = array(1,1,2,2,3); //array containing numbers pool

for each number in pool as numA
{

for each number in pool as numB
{
if numB = numA + 1 then ... //you've found a match, loop again looking for another match.
}
}


It's not direct code since you seem to want a nudge/suggestion more than just an answer