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) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | -4 |
| 5 | 1 |
| 6 | 1 |
| 7 | 21 |
| 8 | 21 |
| 9 | 1 |
| 10 | 1 |
| 11 | -104 |
| 12 | 546 |
| 13 | -104 |
| 14 | 1 |
| 15 | 1 |
| 16 | 521 |
| 17 | 13546 |
| 18 | 13546 |
| 19 | 521 |
| 20 | 1 |
| 21 | 1 |
| 22 | -2604 |
| 23 | 339171 |
| 24 | -1679704 |
| 25 | 339171 |
| 26 | -2604 |
| 27 | 1 |
| 28 | 1 |
| 29 | 13021 |
| 30 | 8476671 |
| 31 | 210302171 |
| 32 | 210302171 |
| 33 | 8476671 |
| 34 | 13021 |
| 35 | 1 |
| 36 | 1 |
| 37 | -65104 |
| 38 | 211929796 |
| 39 | -26279294704 |
| 40 | 131649159046 |