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 | 1 |
| 3 | 2 |
| 4 | 6 |
| 5 | 20 |
| 6 | 69 |
| 7 | 270 |
| 8 | 1026 |
| 9 | 4120 |
| 10 | 16794 |
| 11 | 70230 |
| 12 | 298306 |
| 13 | 1288912 |
| 14 | 5642559 |
| 15 | 25007756 |
| 16 | 111998920 |
| 17 | 506348902 |
| 18 | 2308338456 |
| 19 | 10602357346 |
| 20 | 49026021552 |
| 21 | 228085486580 |
| 22 | 1067020210339 |
| 23 | 5016982766202 |
| 24 | 23698640081356 |
| 25 | 112422573858292 |
| 26 | 535414026652828 |
| 27 | 2559204304109868 |