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A **Duffinian number** is a composite number **k** that is relatively prime to its sigma sum **σ**.

*The sigma sum of **k** is the sum of the divisors of **k**.*

E.G.

**161** is a **Duffinian number**.

* It is composite. (7 × 23)
* The sigma sum **192** (1 + 7 + 23 + 161) is relatively prime to **161**.

Duffinian numbers are very common.

It is not uncommon for two consecutive integers to be Duffinian (a Duffinian twin) (8, 9), (35, 36), (49, 50), etc.

Less common are Duffinian triplets; three consecutive Duffinian numbers. (63, 64, 65), (323, 324, 325), etc.

Much, much less common are Duffinian quadruplets and quintuplets. The first Duffinian quintuplet is (202605639573839041, 202605639573839042, 202605639573839043, 202605639573839044, 202605639573839045).

It is not possible to have six consecutive Duffinian numbers

Task

* Find and show the first 50 Duffinian numbers.
* Find and show at least the first 15 Duffinian triplets.

See also

* Numbers Aplenty - Duffinian numbers * OEIS:A003624 - Duffinian numbers: composite numbers k relatively prime to sigma(k)
assistant
```
use Prime::Factor;

my @duffinians = lazy (3..*).hyper.grep: { !.is-prime && $_ gcd .&divisors.sum == 1 };

put "First 50 Duffinian numbers:\n" ~
@duffinians[^50].batch(10)».fmt("%3d").join: "\n";

put "\nFirst 40 Duffinian triplets:\n" ~
    ((^∞).grep: -> $n { (@duffinians[$n] + 1 == @duffinians[$n + 1]) && (@duffinians[$n] + 2 == @duffinians[$n + 2]) })[^40]\
    .map( { "({@duffinians[$_ .. $_+2].join: ', '})" } ).batch(4)».fmt("%-24s").join: "\n";

```

Output:

```
First 50 Duffinian numbers:
  4   8   9  16  21  25  27  32  35  36
 39  49  50  55  57  63  64  65  75  77
 81  85  93  98 100 111 115 119 121 125
128 129 133 143 144 155 161 169 171 175
183 185 187 189 201 203 205 209 215 217

First 40 Duffinian triplets:
(63, 64, 65)             (323, 324, 325)          (511, 512, 513)          (721, 722, 723)         
(899, 900, 901)          (1443, 1444, 1445)       (2303, 2304, 2305)       (2449, 2450, 2451)      
(3599, 3600, 3601)       (3871, 3872, 3873)       (5183, 5184, 5185)       (5617, 5618, 5619)      
(6049, 6050, 6051)       (6399, 6400, 6401)       (8449, 8450, 8451)       (10081, 10082, 10083)   
(10403, 10404, 10405)    (11663, 11664, 11665)    (12481, 12482, 12483)    (13447, 13448, 13449)   
(13777, 13778, 13779)    (15841, 15842, 15843)    (17423, 17424, 17425)    (19043, 19044, 19045)   
(26911, 26912, 26913)    (30275, 30276, 30277)    (36863, 36864, 36865)    (42631, 42632, 42633)   
(46655, 46656, 46657)    (47523, 47524, 47525)    (53137, 53138, 53139)    (58563, 58564, 58565)   
(72961, 72962, 72963)    (76175, 76176, 76177)    (79523, 79524, 79525)    (84099, 84100, 84101)   
(86527, 86528, 86529)    (94177, 94178, 94179)    (108899, 108900, 108901) (121103, 121104, 121105)
```