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) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 8 |
| 4 | 64 |
| 5 | 540 |
| 6 | 4320 |
| 7 | 35008 |
| 8 | 280064 |
| 9 | 2244152 |
| 10 | 17955008 |
| 11 | 143670304 |
| 12 | 1149362432 |
| 13 | 9195171392 |
| 14 | 73561371136 |
| 15 | 588492929536 |
| 16 | 4707943678208 |
| 17 | 37663565234758 |
| 18 | 301308521878064 |
| 19 | 2410468302643136 |
| 20 | 19283746421145088 |
| 21 | 154269972376667232 |