For this case, the pattern to follow is given by:
 

 Where, 
 n: number of rows 
 an: number of total seats. 
 We have then that for row number 10, we must replace the value of n = 10 in the given formula. 
 We have then: 
 

 For the rest of the rows we repeat the procedure obtaining: 
 1 37 
 2 40 
 3 43 
 4 46 
 5 49 
 6 52 
 7 55 
 8 58 
 9 61 
 10 64 
 Adding the number of seats in each row we obtain: 
 Total = 505 
 Answer: 
 The total number of seats in the first 10 rows is: 
 Total = 505