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 | 0 |
| 1 | 1 |
| 2 | 2 |
| 3 | 9 |
| 4 | 32 |
| 5 | 170 |
| 6 | 1164 |
| 7 | 7434 |
| 8 | 62880 |
| 9 | 582336 |
| 10 | 5875200 |
| 11 | 60041520 |
| 12 | 841501440 |
| 13 | 9440926560 |
| 14 | 141618778560 |
| 15 | 2222190784800 |
| 16 | 34862691548160 |
| 17 | 543348318159360 |
| 18 | 11173101312844800 |
| 19 | 186494289764106240 |
| 20 | 4219768887634944000 |
| 21 | 86094733814301542400 |
| 22 | 1834643656963469721600 |