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 | 0 |
| 1 | 1 |
| 2 | 6 |
| 3 | 27 |
| 4 | 120 |
| 5 | 560 |
| 6 | 2778 |
| 7 | 14665 |
| 8 | 82232 |
| 9 | 488403 |
| 10 | 3062980 |
| 11 | 20221520 |
| 12 | 140134404 |
| 13 | 1016698813 |
| 14 | 7703878042 |
| 15 | 60833235795 |
| 16 | 499592325152 |
| 17 | 4259301450652 |
| 18 | 37634032670886 |
| 19 | 344092369602461 |
| 20 | 3250925202629100 |