### topaa's blog

By topaa, history, 2 months ago,

Hi, This is my first blog. I encountered a problem PAROVI few days ago, but I am not able to solve it. Any ideas on how to proceed? Thankyou.

• +10

 » 2 months ago, # |   +1 Define by $f(l, r)$ the number of sets of pairs of relatively prime integers of $l, l + 1, \ldots, r$, and by $g(l, r)$ the number of sets of pairs of relatively prime integers of $l, l + 1, \ldots, r$ such that there is no $x$ among $l + 1, \ldots, r$ satisfying Slavko's constraint. Then we have the equality $g(l, r) = f(l, r) - \displaystyle \sum_{k = l}^{r - 1} g(l, k) f(k + 1, r).$
•  » » 2 months ago, # ^ | ← Rev. 2 →   0 Thanks. One small question, what should be g(i,i) equal to? Do we have to consider here that we can't construct a pair using same number and also empty sets are not allowed? In that case g(i,i) should be zero. But my code works only with g(i,i)=1. My AC submission
 » 2 months ago, # |   0 124755941 could you please explain me this question ...