229, 361, 493, and 625 are in arithmetic progression:

361 – 229 = 493 – 361 = 625 – 493 = 132

and the number of divisors of each is also in arithmetic progression:

n ……. divisors

229 ….. 2 (1 229)

361 ….. 3 (1 19 361)

493 ….. 4 (1 17 29 493)

625 ….. 5 (1 5 25 125 625)

Can you find another quadruplet of 3-digit numbers?

a quadruplet of 4-digit numbers?

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