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 | 1 |
| 2 | 6 |
| 3 | 42 |
| 4 | 392 |
| 5 | 4600 |
| 6 | 64752 |
| 7 | 1063216 |
| 8 | 19952256 |
| 9 | 421227648 |
| 10 | 9880951040 |
| 11 | 254960721664 |
| 12 | 7176891675648 |
| 13 | 218857588139008 |
| 14 | 7187394935347200 |
| 15 | 252897556424140800 |
| 16 | 9491754142468702208 |
| 17 | 378509920569294684160 |
| 18 | 15982018774576565649408 |
| 19 | 712306819507400060502016 |