View Compilation Error

0_0_5461982_1699.cpp: In function `void catalan()':
0_0_5461982_1699.cpp:10: error: `b' undeclared (first use this function)
0_0_5461982_1699.cpp:10: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_5461982_1699.cpp: In function `int main()':
0_0_5461982_1699.cpp:45: error: `b' undeclared (first use this function)