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 | 2 |
| 2 | 6 |
| 3 | 18 |
| 4 | 56 |
| 5 | 170 |
| 6 | 492 |
| 7 | 1358 |
| 8 | 3600 |
| 9 | 9234 |
| 10 | 23060 |
| 11 | 56342 |
| 12 | 135192 |
| 13 | 319514 |
| 14 | 745500 |
| 15 | 1720350 |
| 16 | 3932192 |
| 17 | 8912930 |
| 18 | 20054052 |
| 19 | 44826662 |
| 20 | 99614760 |
| 21 | 220201002 |
| 22 | 484442156 |
| 23 | 1061158958 |
| 24 | 2315255856 |
| 25 | 5033164850 |
| 26 | 10905190452 |
| 27 | 23555211318 |
| 28 | 50734301240 |
| 29 | 108984795194 |
| 30 | 233538846780 |