Undefined method for 'n' in ruby while loop -

i trying write algorithm solve math problem Σ n = 1 49 of n(n+1). keep getting error "undefined method 'n' main object"

def solver(n)   sum = 0   while n < 49     temp = n(n+1)     n+=1     sum = sum + temp   end   return sum end  puts solver(1)

instead of:

temp = n(n+1)

put:

temp = n*(n+1)

Camp