This is a series of Armstrong numbers (narcissistic numbers): numbers equal to the sum of their own digits each raised to the power of the number of digits. 153=1^3+5^3+3^3, 370=3^3+7^3+0^3, 371=3^3+7^3+1^3, 407=4^3+0^3+7^3. 269 is not an Armstrong number (2^3+6^3+9^3=953≠269).