@MartinSleziak Since nobody objected, I went with Xander Henderson's suggestion and cast close votes with the oldest post as the duplicate target. I have also edited the title:
How do you solve a recurrence with a summation function inside: $t(n) = 1 + \sum\limits_{j=0}^{n-1} t(j)$. (In order to make the title more descriptive - so that if the post is shown in some list of questions, the contend is clearer directly from the title.)