Here i found a subtle pattern too it has to do with the ending digits and the corresponding sum total difference number..I am going to list some draws in order to better explain what i mean...

1.  15= +2

2.  17= -4

3.  13= 0

4.  13= -4

5.  9= +5

6.  14= -7

7.  7= +13

8.  20= -2

9.  18= +2

10.  20= -6

11.  14= +4

12.  18= -1

13.  17= +3

14.  20 = -2

15.  18= +3

16.  21= -4

17.  17= -3

18.  14= -6

19.  8= +5

20.  13= +2

21.  15= -3

Let me explain what ending digit is...1,11,21,31 have ending digit of 1 (one)....2,12,22,32 have ending digit of 2 (two)....3,13,23,33 have ending digit of 3 (three)....4,14,24,34 have ending digit of 4 (four)....5,15,25,35 have ending digit of 5 (five)...6,16,26,36 have ending digit of 6 (six)....7,17,27 have ending digit of 7 (seven)....8,18,28 have ending digit of 8 (eight)...9,19,29 have ending digit of 9 (nine)...0,10,20,30 have ending digit of 0 (zero)....

Now that you know what ending digits are here is the pattern...I found 1 pattern so far...It applies to pick3 and i have yet to see if it applies to pick4...

Subtle Pattern #12: The sum total ending digit doesn't match the ending digit of the sum total difference...In the example i showed you above you see 15= +2 but you will not see 15=+5 or -5...In the example i showed you above you saw 17=-4 but you will not see 17=+7 or -7...In the example i showed you above you see 13= 0 but you will not see 13= +3 or -3...If you indeed see it happen, it rarely does so...