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 | 5 |
| 3 | 35 |
| 4 | 239 |
| 5 | 1799 |
| 6 | 15119 |
| 7 | 141119 |
| 8 | 1451519 |
| 9 | 16329599 |
| 10 | 199583999 |
| 11 | 2634508799 |
| 12 | 37362124799 |
| 13 | 566658892799 |
| 14 | 9153720575999 |
| 15 | 156920924159999 |
| 16 | 2845499424767999 |
| 17 | 54420176498687999 |
| 18 | 1094805903679487999 |
| 19 | 23112569077678079999 |
| 20 | 510909421717094399999 |