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 | 0 |
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 0 |
| 6 | 1 |
| 7 | 2 |
| 8 | 6 |
| 9 | 22 |
| 10 | 86 |
| 11 | 342 |
| 12 | 1366 |
| 13 | 5462 |
| 14 | 21591 |
| 15 | 85600 |
| 16 | 339616 |
| 17 | 1347632 |
| 18 | 5347632 |
| 19 | 21219888 |
| 20 | 84199984 |
| 21 | 334092848 |
| 22 | 1325649969 |
| 23 | 5260075594 |
| 24 | 20871578510 |
| 25 | 82816815054 |
| 26 | 328610657230 |
| 27 | 1303901211854 |
| 28 | 5173777051854 |
| 29 | 20529140314318 |