The general term is given by 3r+1+(-1)^r+1

So by substituting r=0,1,2,3.... I get a sequence like this: 0, 5, 6, 11, 12, 17, 18.....

It seems to form some pattern. So i wonder, can i deduce the general term with only the sequence? How?

Please kindly elaborate more if possible because i really keen to learn how.