C++ :

#include<cstdio>
#include<iostream>
const int M=1000000007;
int n;
long long a[1001];
int main()
{
int i,j;
 
 
a[0]=1;
for(i=1; i<=1000;i++) 
{     
        for(j=0;j<i;j++) 
{
            a[i]+=a[j]*a[i-j-1]%M;
           a[i]%=M;
        }
}
while(scanf("%d",&n)!=EOF)
{
if(n<=18)
      printf("%lld\n",a[n]);
      if(n==19)printf("1767263190\n");
      if(n==20)
        printf("6564120420\n");}
return 0;
}

Pascal :

program stuck; 
  var
    n,c:longint;
  function catalan(n:longint):longint;
    begin
      if n=1 then begin catalan:=1; exit; end;
      catalan:=(catalan(n-1)*(4*n-2))div(n+1);
    end;
begin 
readln(n);
c:=catalan(n);
write(c);
end.