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 | 9 |
| 3 | 45 |
| 4 | 201 |
| 5 | 735 |
| 6 | 2517 |
| 7 | 7785 |
| 8 | 22857 |
| 9 | 63024 |
| 10 | 166819 |
| 11 | 422537 |
| 12 | 1035971 |
| 13 | 2456694 |
| 14 | 5672347 |
| 15 | 12756334 |
| 16 | 28053280 |
| 17 | 60371967 |
| 18 | 127479247 |
| 19 | 264311585 |
| 20 | 539102751 |
| 21 | 1082474167 |
| 22 | 2142579168 |
| 23 | 4183251750 |
| 24 | 8064722973 |
| 25 | 15360809911 |
| 26 | 28928858208 |
| 27 | 53896616704 |
| 28 | 99398216733 |