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) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 2 |
| 4 | 4 |
| 5 | 16 |
| 6 | 36 |
| 7 | 128 |
| 8 | 440 |
| 9 | 1706 |
| 10 | 6560 |
| 11 | 24576 |
| 12 | 90046 |
| 13 | 327680 |
| 14 | 1197824 |
| 15 | 4438966 |
| 16 | 16645120 |
| 17 | 62914560 |
| 18 | 238609052 |
| 19 | 905969664 |
| 20 | 3442670796 |
| 21 | 13102206738 |
| 22 | 49977704448 |
| 23 | 191126044672 |
| 24 | 732649663000 |
| 25 | 2814062572336 |
| 26 | 10825960652800 |
| 27 | 41705086880768 |
| 28 | 160862475611574 |