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 | 1 |
| 1 | 9 |
| 2 | 153 |
| 3 | 2925 |
| 4 | 58905 |
| 5 | 1221759 |
| 6 | 25827165 |
| 7 | 553270671 |
| 8 | 11969016345 |
| 9 | 260887834350 |
| 10 | 5720645481903 |
| 11 | 126050526132804 |
| 12 | 2788629694000605 |
| 13 | 61902409203193230 |
| 14 | 1378095785451705375 |
| 15 | 30756373941461374800 |
| 16 | 687917389635036844569 |
| 17 | 15415916972482007401455 |
| 18 | 346051021610256116115150 |