This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | -1 |
| 3 | 0 |
| 4 | 1 |
| 5 | 0 |
| 6 | -1 |
| 7 | -2 |
| 8 | -1 |
| 9 | 8 |
| 10 | 25 |
| 11 | 26 |
| 12 | -111 |
| 13 | -590 |
| 14 | -1419 |
| 15 | 456 |
| 16 | 21639 |
| 17 | 99822 |
| 18 | 202875 |
| 19 | -545926 |
| 20 | -7583365 |
| 21 | -36354050 |
| 22 | -71015561 |
| 23 | 372995254 |
| 24 | 4834925399 |
| 25 | 25950214696 |
| 26 | 60006459617 |
| 27 | -337120306782 |
| 28 | -5124389194155 |
| 29 | -33147265576814 |