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 | 15 |
| 3 | 83 |
| 4 | 486 |
| 5 | 2937 |
| 6 | 18109 |
| 7 | 113220 |
| 8 | 715122 |
| 9 | 4552229 |
| 10 | 29156985 |
| 11 | 187683795 |
| 12 | 1213110600 |
| 13 | 7868238588 |
| 14 | 51184173036 |
| 15 | 333809308696 |
| 16 | 2181842704602 |
| 17 | 14288748463485 |
| 18 | 93737673347185 |
| 19 | 615889045662345 |
| 20 | 4052198020223430 |
| 21 | 26694405836621985 |
| 22 | 176052003674681925 |