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 | 0 |
| 1 | 1 |
| 2 | 2049 |
| 3 | 179196 |
| 4 | 4373500 |
| 5 | 53201625 |
| 6 | 415998681 |
| 7 | 2393325424 |
| 8 | 10983260016 |
| 9 | 42364319625 |
| 10 | 142364319625 |
| 11 | 427675990236 |
| 12 | 1170684360924 |
| 13 | 2962844754961 |
| 14 | 7012409924625 |
| 15 | 15662165784000 |
| 16 | 33254351828416 |
| 17 | 67526248136049 |
| 18 | 131794658215281 |
| 19 | 248284917113500 |
| 20 | 453084917113500 |