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 | 6 |
| 2 | 15 |
| 3 | 70 |
| 4 | 315 |
| 5 | 1554 |
| 6 | 7735 |
| 7 | 39990 |
| 8 | 209790 |
| 9 | 1119720 |
| 10 | 6045837 |
| 11 | 32981550 |
| 12 | 181394535 |
| 13 | 1004668770 |
| 14 | 5597420295 |
| 15 | 31345665106 |
| 16 | 176319264240 |
| 17 | 995685849690 |
| 18 | 5642219252460 |
| 19 | 32071565263710 |
| 20 | 182807918979777 |