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 | 4 |
| 2 | 36 |
| 3 | 135 |
| 4 | 620 |
| 5 | 3637 |
| 6 | 17450 |
| 7 | 86139 |
| 8 | 451210 |
| 9 | 2267574 |
| 10 | 11420744 |
| 11 | 58323254 |
| 12 | 295406628 |
| 13 | 1495704814 |
| 14 | 7596893701 |
| 15 | 38524719319 |
| 16 | 195316135549 |
| 17 | 990921152875 |
| 18 | 5025881864695 |
| 19 | 25488754160616 |
| 20 | 129285719478533 |
| 21 | 655737002374833 |