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 | 0 |
| 5 | 0 |
| 6 | 3 |
| 7 | 5 |
| 8 | 20 |
| 9 | 56 |
| 10 | 112 |
| 11 | 268 |
| 12 | 618 |
| 13 | 1922 |
| 14 | 8531 |
| 15 | 29021 |
| 16 | 100407 |
| 17 | 321531 |
| 18 | 899618 |
| 19 | 2937312 |
| 20 | 9295401 |
| 21 | 31615059 |
| 22 | 117365818 |
| 23 | 403433963 |
| 24 | 1417579281 |
| 25 | 4848439367 |
| 26 | 15960316056 |
| 27 | 55180971700 |
| 28 | 190251417034 |
| 29 | 670818005444 |
| 30 | 2429973932322 |