Task 1: "Chowla Numbers

Write a script to generate first 20 Chowla Numbers, named after,
Sarvadaman D. S. Chowla, a London born Indian American mathematician. It
is defined as:

C(n) = sum of divisors of n except 1 and n

NOTE: Updated the above definition as suggested by Abigail [2021/04/19 18:40].

Output:

0, 0, 0, 2, 0, 5, 0, 6, 3, 7, 0, 15, 0, 9, 8, 14, 0, 20, 0, 21
"

My notes: easy and fun.


Task 2: "Four Squares Puzzle

You are given four squares as below with numbers named a,b,c,d,e,f,g.

              (1)                    (3)
        ===============     ===============
        |             |     |             |
        |     a       |     |     e       |
        |             |(2)  |             | (4)
        |         ---------------     --------------
        |         |   |     |   |     |   |        |
        |         | b |     | d |     | f |        |
        |         |   |     |   |     |   |        |
        |         |   |     |   |     |   |        |
        ==========|====     ====|==========        |
                  |      c      |     |     g      |
                  |             |     |            |
                  |             |     |            |
                  ---------------     --------------

Write a script to place the given unique numbers in the square box so
that sum of numbers in each box is the same.

Example

Input: 1,2,3,4,5,6,7

Output:

    a = 6
    b = 4
    c = 1
    d = 5
    e = 2
    f = 3
    g = 7

    Box 1: a + b = 6 + 4 = 10
    Box 2: b + c + d = 4 + 1 + 5 = 10
    Box 3: d + e + f = 5 + 2 + 3 = 10
    Box 4: f + g = 3 + 7 = 10
"

My notes: sounds simple enough.  Find a,b,c,d,e,f st a+b = b+c+d = d+e+f = f+g
Of course, we'll need to try all permutations of the values given.  There
are lots of CPAN modules (eg. Algorithm::Permute), but here I decided to
generate the permutations myself via Rosetta Stone code..