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 | 3 |
| 3 | 9 |
| 4 | 31 |
| 5 | 111 |
| 6 | 453 |
| 7 | 2059 |
| 8 | 10571 |
| 9 | 60651 |
| 10 | 386253 |
| 11 | 2704659 |
| 12 | 20661411 |
| 13 | 170990691 |
| 14 | 1523975053 |
| 15 | 14552848059 |
| 16 | 148234015051 |
| 17 | 1604267622731 |
| 18 | 18383552327853 |
| 19 | 222363321668259 |
| 20 | 2831217743661491 |
| 21 | 37850593064646771 |
| 22 | 530121590756400653 |