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 | 7 |
| 2 | 42 |
| 3 | 336 |
| 4 | 2352 |
| 5 | 16800 |
| 6 | 117264 |
| 7 | 823536 |
| 8 | 5762400 |
| 9 | 40353264 |
| 10 | 282458400 |
| 11 | 1977326736 |
| 12 | 13841167200 |
| 13 | 96889010400 |
| 14 | 678222249264 |
| 15 | 4747561492800 |
| 16 | 33232924804800 |
| 17 | 232630513987200 |
| 18 | 1628413557439536 |
| 19 | 11398895185373136 |
| 20 | 79792266015134400 |
| 21 | 558545864082460128 |