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 | 1 |
| 2 | 5 |
| 3 | 48 |
| 4 | 697 |
| 5 | 13640 |
| 6 | 336771 |
| 7 | 10053778 |
| 8 | 352334753 |
| 9 | 14183529480 |
| 10 | 645073504435 |
| 11 | 32715111226886 |
| 12 | 1830671281889649 |
| 13 | 112049330303532388 |
| 14 | 7446824171300128811 |
| 15 | 534068807341887943770 |
| 16 | 41111698162393482004801 |
| 17 | 3381089519620006418116976 |
| 18 | 295869084136630532211207843 |