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 | 0 |
| 2 | 1 |
| 3 | 4 |
| 4 | 9 |
| 5 | 30 |
| 6 | 84 |
| 7 | 202 |
| 8 | 528 |
| 9 | 1320 |
| 10 | 3144 |
| 11 | 7568 |
| 12 | 17888 |
| 13 | 41472 |
| 14 | 95760 |
| 15 | 218880 |
| 16 | 495344 |
| 17 | 1114656 |
| 18 | 2491584 |
| 19 | 5534688 |
| 20 | 12234880 |
| 21 | 26916736 |
| 22 | 58954752 |
| 23 | 128629248 |
| 24 | 279628800 |
| 25 | 605847808 |
| 26 | 1308632832 |
| 27 | 2818593792 |
| 28 | 6054720768 |
| 29 | 12974405120 |
| 30 | 27738383360 |
| 31 | 59175129600 |