2+3+5+6+8+9+......+(3n-1)+(3n) a.p.
separate it into
2+5+8+...
and
3+6+9+...
add the two sequences together. Each is easy to figure, right?
Or, make it a single sequence
6n-1 ...
5+11+17+...
2+5+8+...
and
3+6+9+...
add the two sequences together. Each is easy to figure, right?
Or, make it a single sequence
6n-1 ...
5+11+17+...