Quote:
Originally Posted by issybird
174, 202, 206, 218.....
It seems as if you multiply the digits of each number (ignoring 0), and then add the product to the number. But that doesn't explain how you got from 5 to 10. So I think what you do is square the product of the digits and then divide it by the product before adding it back, which would do it. But I don't have a good reason for ignoring those zeroes. Best I can do.
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Your first idea is spot on. Zero is ignored, because if you don't the series quickly become uninteresting!
5 -> 10 follows the same rules as the others. The product of the digits of 5 is 5. 5 + 5 = 10
Over to you!