C++ :: Print Asterisks To Correspond To Program

i have to make two functions one recursion that ask the user to enter number of rows and i use recursion to tell him how many pins there are ex. user enters 5 there are 15 pins. I did this function now i need a function that prints an asterisk triangle for my recursion function so for 15 it should look like this

*
* *
* * *
* * * *
* * * * *

i tried many times but can't make it descend like that i can only get like a right triangle..the hard part is that it goes with the users number so if they enter 3 for example it should be 3 rows.

int pins(int n){
if(n==0){
return 0;

[code]....