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 | 0 |
| 2 | 3 |
| 3 | 1 |
| 4 | 21 |
| 5 | 26 |
| 6 | 215 |
| 7 | 498 |
| 8 | 2821 |
| 9 | 9040 |
| 10 | 43695 |
| 11 | 165375 |
| 12 | 752785 |
| 13 | 3101970 |
| 14 | 13881803 |
| 15 | 59837183 |
| 16 | 267860685 |
| 17 | 1184749704 |
| 18 | 5337504263 |
| 19 | 23996776941 |
| 20 | 108964583121 |
| 21 | 495544446410 |
| 22 | 2267450194443 |
| 23 | 10402298479276 |
| 24 | 47926692348121 |