Here's the patterns of 3, 6 and 9 and also the repdigits of 3, 6 and 9.
 
Repeat of 3's and the Multiplication of 34 and 37
 
3 x 34 = 102  33 x 34 = 1122  333 x 34 = 11322  3333 x 34 = 113322  33333 x 34 = 1133322  333333 x 34 = 11333322
3 x 37 = 111  33 x 37 = 1221  333 x 37 = 12321  3333 x 37 = 123321  33333 x 37 = 1233321  333333 x 37 = 12333321
 
Repeat of 6's
 
6 x 34 = 203  66 x 34 = 2233  666 x 34 = 22633  6666 x 34 = 226633  66666 x 34 = 2266633  666666 x 34 = 22666633
6 x 37 = 222  66 x 37 = 2332  666 x 37 = 23632  6666 x 37 = 236632  66666 x 37 = 2366632  666666 x 37 = 23666632
 
Repeat of 9's
 
9 x 34 = 306  99 x 34 = 3366  999 x 34 = 33966  9999 x 34 = 339966  99999 x 34 = 3399966  999999 x 34 = 33999966
9 x 37 = 333  99 x 37 = 3663  999 x 37 = 36963  9999 x 37 = 369963  99999 x 37 = 3699963  999999 x 37 = 36999963
 
Now according to the triangular numbers.... 21 is the 6th triangle, 2211 is the 66th triangle, 222111 is the 666th triangle, 22221111 is the 6666th triangle.
 
Any thoughts or comments?
 
Sara Reynolds