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 | 9 |
| 3 | 58 |
| 4 | 336 |
| 5 | 1853 |
| 6 | 9945 |
| 7 | 52487 |
| 8 | 273939 |
| 9 | 1418567 |
| 10 | 7303791 |
| 11 | 37441560 |
| 12 | 191287254 |
| 13 | 974642943 |
| 14 | 4955123955 |
| 15 | 25146686730 |
| 16 | 127424717400 |
| 17 | 644873878895 |
| 18 | 3260055588615 |
| 19 | 16465301636090 |
| 20 | 83092583965020 |
| 21 | 419031686115875 |