If we take out 1, we will get a arithmetic progression: 1993, 1992, 199 1, 1990, …; In the original sequence, if a number 1 appears in a set of three numbers, then the number 1993 is 1993÷3=664… 1. You can use a number 1 to divide into 664 groups, that is, 665 numbers 1, and the rest are 18.

So the sum of the former 1993 is:

1×665+(666+ 1993)× 1328÷2

=665+2659× 1328÷2

=665+ 1765576

= 176624 1.

Is it okay? Please agree if you can, thank you! !