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 | 3 |
| 2 | 21 |
| 3 | 165 |
| 4 | 1380 |
| 5 | 11982 |
| 6 | 106626 |
| 7 | 965442 |
| 8 | 8854725 |
| 9 | 82022115 |
| 10 | 765787773 |
| 11 | 7195638909 |
| 12 | 67973370618 |
| 13 | 644991134880 |
| 14 | 6143707229880 |
| 15 | 58714212503784 |
| 16 | 562741793028282 |
| 17 | 5407273475087934 |
| 18 | 52074626299010130 |
| 19 | 502513862912425650 |
| 20 | 4857975310180620720 |