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 | 1 |
| 3 | 1 |
| 4 | 10 |
| 5 | 26 |
| 6 | 276 |
| 7 | 1212 |
| 8 | 14736 |
| 9 | 92304 |
| 10 | 1285920 |
| 11 | 10516320 |
| 12 | 166112640 |
| 13 | 1680462720 |
| 14 | 29753498880 |
| 15 | 359124192000 |
| 16 | 7053661440000 |
| 17 | 98989454592000 |
| 18 | 2137497610752000 |
| 19 | 34210080898560000 |
| 20 | 805846718380032000 |
| 21 | 14489879077804032000 |
| 22 | 369868281883398144000 |