Depends where you define the first one to be.
Starting at 0:0, 3, 6, 9, 12, 15, 18, 21, 24, 27, 30Starting at 3:3, 6, 9, 12, 15, 18, 21, 24, 27, 30, 33
3, 6, 9, 12, 15, 18, 21, 24, 27, 30, 33, 36, 39, 42, 45, 48, 51, 54, 57, 60, 63, 66, 69, 72, 75, 78, 81, 84, 87, 90, 93, 96, 99, 102, 105, 108, 111, 114, 117, 120, 123, 126, 129, 132, 135, 138, 141,...
3,6,9,12,15,18,21,24,27,30,33,36,39,42,45,48,51,54,57,60,63. 3,6,9,12,15,18,21,24,27,30,33,36,39,42,45,48,51,54,57,60,63.
3, 6, 9, 12, 15, 18
3x1=3 3x2=6 3x3=9 3x4=12 3x5=15 3x6=18
0,3,6,9,12,15,18,21,24,27Edit:0 is not normally considered the first multiple.