Answer: 3
step-by-step example:■ The 24th value of the sequence (a24) is 501
■ Sample of the first ten numbers in the sequence: 18, 39, 60, 81, 102, 123, 144, 165, 186, 207
■ Sum of all numbers until the 24th: 6228
■ The mean value of the series: 259.5
■ Standard deviation: 145.3659