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 | 4 |
| 3 | 8 |
| 4 | 20 |
| 5 | 40 |
| 6 | 120 |
| 7 | 520 |
| 8 | 1560 |
| 9 | 8840 |
| 10 | 26520 |
| 11 | 185640 |
| 12 | 769080 |
| 13 | 5383560 |
| 14 | 28455960 |
| 15 | 199191720 |
| 16 | 1166694360 |
| 17 | 8166860520 |
| 18 | 61834801080 |
| 19 | 432843607560 |
| 20 | 3771922865880 |
| 21 | 26403460061160 |
| 22 | 275350369209240 |
| 23 | 1927452584464680 |
| 24 | 21201978429111480 |
| 25 | 171543280017356520 |