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 | 1 |
| 3 | 0 |
| 4 | 0 |
| 5 | 3 |
| 6 | 3 |
| 7 | 0 |
| 8 | 1 |
| 9 | 63 |
| 10 | 662 |
| 11 | 2400 |
| 12 | 3900 |
| 13 | 2940 |
| 14 | 840 |
| 15 | 0 |
| 16 | 94 |
| 17 | 97692 |
| 18 | 10308758 |
| 19 | 337560150 |
| 20 | 5098740090 |
| 21 | 42976836210 |
| 22 | 224685801060 |
| 23 | 775389028050 |
| 24 | 1830791421900 |
| 25 | 3007909258200 |
| 26 | 3439214024400 |
| 27 | 2685727044000 |
| 28 | 1366701336000 |
| 29 | 408648240000 |
| 30 | 54486432000 |