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 | 2 |
| 5 | 6 |
| 6 | 20 |
| 7 | 50 |
| 8 | 126 |
| 9 | 288 |
| 10 | 654 |
| 11 | 1422 |
| 12 | 3068 |
| 13 | 6474 |
| 14 | 13574 |
| 15 | 28112 |
| 16 | 57942 |
| 17 | 118566 |
| 18 | 241788 |
| 19 | 490914 |
| 20 | 994334 |
| 21 | 2008512 |
| 22 | 4050398 |
| 23 | 8154014 |
| 24 | 16396668 |
| 25 | 32935194 |
| 26 | 66104982 |
| 27 | 132586416 |
| 28 | 265792070 |
| 29 | 532579830 |
| 30 | 1066790972 |