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 | 0 |
| 2 | 0 |
| 3 | 2 |
| 4 | 7 |
| 5 | 36 |
| 6 | 225 |
| 7 | 1610 |
| 8 | 13104 |
| 9 | 119548 |
| 10 | 1208583 |
| 11 | 13413960 |
| 12 | 162176105 |
| 13 | 2121703324 |
| 14 | 29866022640 |
| 15 | 450112042926 |
| 16 | 7231658709455 |
| 17 | 123388310103660 |
| 18 | 2228221240575337 |
| 19 | 42459591881035062 |
| 20 | 851420058861276576 |
| 21 | 17922280827967843160 |
| 22 | 395141598274153826095 |