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 | 5 |
| 2 | 55 |
| 3 | 430 |
| 4 | 3605 |
| 5 | 25980 |
| 6 | 203280 |
| 7 | 1417530 |
| 8 | 10373080 |
| 9 | 71595830 |
| 10 | 501688880 |
| 11 | 3376856755 |
| 12 | 23181027055 |
| 13 | 153326091805 |
| 14 | 1024829902855 |
| 15 | 6713038952355 |
| 16 | 44092634675905 |
| 17 | 284723995000530 |
| 18 | 1845944380173205 |
| 19 | 11791816763005330 |
| 20 | 75485171060740630 |
| 21 | 478105767714603130 |