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 | 2 |
| 3 | 5 |
| 4 | 14 |
| 5 | 42 |
| 6 | 132 |
| 7 | 429 |
| 8 | 1429 |
| 9 | 4851 |
| 10 | 16718 |
| 11 | 58331 |
| 12 | 205632 |
| 13 | 731272 |
| 14 | 2620176 |
| 15 | 9449695 |
| 16 | 34276230 |
| 17 | 124959485 |
| 18 | 457621780 |
| 19 | 1682686509 |
| 20 | 6209928010 |
| 21 | 22993696620 |
| 22 | 85396852670 |
| 23 | 318034472365 |
| 24 | 1187429860461 |
| 25 | 4443824658798 |
| 26 | 16666506959312 |
| 27 | 62632954529054 |