181
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
The first three terms of an arithmetic sequence are 1, 10 and 19, respectively. What is the value of the 21st term?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
181
The first three terms of an arithmetic sequence are 1, 10 and 19, respectively. What is the value of the 21st term?
train