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 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 120 |
| 6 | 720 |
| 7 | 1854 |
| 8 | 4738 |
| 9 | 12072 |
| 10 | 30818 |
| 11 | 79118 |
| 12 | 204448 |
| 13 | 528950 |
| 14 | 1370674 |
| 15 | 3557408 |
| 16 | 9244418 |
| 17 | 24043990 |
| 18 | 62573616 |
| 19 | 162925614 |
| 20 | 424377730 |
| 21 | 1105703640 |
| 22 | 2881483458 |
| 23 | 7510389278 |
| 24 | 19577689120 |
| 25 | 51038756326 |
| 26 | 133066443346 |
| 27 | 346944079632 |
| 28 | 904622495746 |
| 29 | 2358783572710 |
| 30 | 6150613767440 |
| 31 | 16038217209886 |