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 | 9 |
| 3 | 30 |
| 4 | 99 |
| 5 | 330 |
| 6 | 1098 |
| 7 | 3660 |
| 8 | 12195 |
| 9 | 40650 |
| 10 | 135486 |
| 11 | 451620 |
| 12 | 1505358 |
| 13 | 5017860 |
| 14 | 16726068 |
| 15 | 55753560 |
| 16 | 185844771 |
| 17 | 619482570 |
| 18 | 2064940470 |
| 19 | 6883134900 |
| 20 | 22943778138 |
| 21 | 76479260460 |
| 22 | 254930851404 |
| 23 | 849769504680 |
| 24 | 2832564956814 |