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 | 0 |
| 1 | 3 |
| 2 | 12 |
| 3 | 54 |
| 4 | 240 |
| 5 | 1068 |
| 6 | 4752 |
| 7 | 21144 |
| 8 | 94080 |
| 9 | 418608 |
| 10 | 1862592 |
| 11 | 8287584 |
| 12 | 36875520 |
| 13 | 164077248 |
| 14 | 730060032 |
| 15 | 3248394624 |
| 16 | 14453698560 |
| 17 | 64311583488 |
| 18 | 286153731072 |
| 19 | 1273238091264 |
| 20 | 5665259827200 |
| 21 | 25207515491328 |
| 22 | 112160581619712 |
| 23 | 499057357461504 |
| 24 | 2220550593085440 |
| 25 | 9880317087264768 |
| 26 | 43962369535229952 |