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 | 3 |
| 4 | 25 |
| 5 | 340 |
| 6 | 7026 |
| 7 | 204862 |
| 8 | 8007602 |
| 9 | 404077632 |
| 10 | 25569505628 |
| 11 | 1982619985192 |
| 12 | 184861494417920 |
| 13 | 20406183592852460 |
| 14 | 2631875641089358912 |
| 15 | 392163247878318070876 |
| 16 | 66855512799464487146588 |
| 17 | 12929525365915201064027856 |
| 18 | 2815456378791384288128303192 |