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 | 0 |
| 3 | 0 |
| 4 | 2 |
| 5 | 0 |
| 6 | 0 |
| 7 | 0 |
| 8 | 0 |
| 9 | 0 |
| 10 | 4 |
| 11 | 56 |
| 12 | 172 |
| 13 | 680 |
| 14 | 1348 |
| 15 | 6576 |
| 16 | 34568 |
| 17 | 107624 |
| 18 | 413760 |
| 19 | 1697288 |
| 20 | 8035558 |
| 21 | 37441416 |
| 22 | 192483420 |
| 23 | 1115143224 |