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 | 2 |
| 2 | 10 |
| 3 | 168 |
| 4 | 4290 |
| 5 | 136136 |
| 6 | 4938024 |
| 7 | 196125600 |
| 8 | 8318177010 |
| 9 | 370784099400 |
| 10 | 17184867259560 |
| 11 | 821870841735840 |
| 12 | 40334204896057800 |
| 13 | 2022686389717666848 |
| 14 | 103312949950998743200 |
| 15 | 5360873347802169267840 |
| 16 | 282015983963437605168210 |