Sir base case doubt

if(n==0)
{

return 0;

}

f(n==1)
{

return 2;

}

else if(n==2)
{

return 3;

}

is this base case right??

yes it is right

for n=0 no string
for n=1 : 0 and 1
for n=2 : 00 01 10