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Divisors' sum = square (Posted on 2019-05-27)

The number 22 divisors are 1, 2, 11, 22, which add up to 36, a square.
There are 4 more numbers like that below 100.

List them.

See The Solution Submitted by Ady TZIDON

Rating: 3.0000 (2 votes)

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Puzzle Thoughts

| Comment 8 of 9 |

From OEIS A006532:

"Numbers whose sum of divisors is a square" (located at oeis.org)

we note that :

The required additional 4 numbers are:

66, 70, 81, and 94.

This Sloane series also has a very interesting comment:

"Apart from a(2) ( the second term) all terms are composite."

Edited on June 17, 2022, 12:33 am

Posted by K Sengupta on 2022-06-17 00:25:14

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