To select multiple OIDs, you could just hardcode it like so:
number1 = 25
number2 = 37
'"OID"=' + str(number1) + ' OR "OID"=' + str(number2)
'"OID"=25 OR "OID"=37'
This becomes a problem when you need to select multiple OIDs, so you can use something like below. I've successfully used this as inputs to cursors and select layer by attribute/location, but it can't be used for anything over a few thousand entries as it causes fatal ArcMap crashes. (I'm not sure what the cut off point is.) If you need to be selecting that many OIDs, it's best to write all your data to a list of lists and filter out what you want in Python.
numberlist = [25,37,29,251,17]
'"OID"=' + ' OR "OID"='.join(map(str, numberlist))
'"OID"=25 OR "OID"=37 OR "OID"=29 OR "OID"=251 OR "OID"=17'
As @nmpeterson pointed out, the following is much better and probably doesn't suffer from the crashes:
numberlist = [25,37,29,251,17]
'"OID" IN ({1})'.format(",".join(map(str, numberlist)))
'"OID" IN (25,37,29,251,17)'