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 | 9 |
| 3 | 40 |
| 4 | 190 |
| 5 | 924 |
| 6 | 4578 |
| 7 | 22968 |
| 8 | 116325 |
| 9 | 593450 |
| 10 | 3045185 |
| 11 | 15699840 |
| 12 | 81260816 |
| 13 | 421993040 |
| 14 | 2197653240 |
| 15 | 11472991008 |
| 16 | 60023749566 |
| 17 | 314621200260 |
| 18 | 1651883008050 |
| 19 | 8685998428800 |
| 20 | 45734484854520 |
| 21 | 241098942106440 |
| 22 | 1272406536645660 |