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 | 9 |
| 2 | 74 |
| 3 | 638 |
| 4 | 5944 |
| 5 | 60216 |
| 6 | 662640 |
| 7 | 7893840 |
| 8 | 101378880 |
| 9 | 1397759040 |
| 10 | 20606463360 |
| 11 | 323626665600 |
| 12 | 5395972377600 |
| 13 | 95218662067200 |
| 14 | 1773217155225600 |
| 15 | 34758188233574400 |
| 16 | 715437948072960000 |
| 17 | 15429680577561600000 |
| 18 | 347968129734973440000 |
| 19 | 8190600438533990400000 |