user
Find the numbers **k** whose divisor sum is equal to the divisor sum of **k + 1**.

*Divisor sum is also known as sigma-sum.*

For example

```
   14 has divisors 1, 2, 7, 14 that sum to 24.
   15 has divisors 1, 3, 5, 15 that sum to 24.

```

So 14 is a member of this sequence.

Task

Find the first 25 members of this sequence.

Stretch

Find the first 50 members of this sequence.

See also

:   * **OEIS A002961 - Numbers k such that k and k+1 have same sum of divisors**
assistant
```
use Prime::Factor;
use Lingua::EN::Numbers;

say ++$, ': ', .&comma for (^Inf).hyper.grep( {
    state $next = .&sigma-sum;
    my $test = $next == my $this = ($_ + 1).&sigma-sum;
    $next = $this;
    $test
})[^50];

```

Output:

```
1: 14
2: 206
3: 957
4: 1,334
5: 1,364
6: 1,634
7: 2,685
8: 2,974
9: 4,364
10: 14,841
11: 18,873
12: 19,358
13: 20,145
14: 24,957
15: 33,998
16: 36,566
17: 42,818
18: 56,564
19: 64,665
20: 74,918
21: 79,826
22: 79,833
23: 84,134
24: 92,685
25: 109,214
26: 111,506
27: 116,937
28: 122,073
29: 138,237
30: 147,454
31: 161,001
32: 162,602
33: 166,934
34: 174,717
35: 190,773
36: 193,893
37: 201,597
38: 230,390
39: 274,533
40: 289,454
41: 347,738
42: 383,594
43: 416,577
44: 422,073
45: 430,137
46: 438,993
47: 440,013
48: 445,874
49: 455,373
50: 484,173
```