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 | 4 |
| 2 | 23 |
| 3 | 106 |
| 4 | 473 |
| 5 | 1939 |
| 6 | 7618 |
| 7 | 28703 |
| 8 | 105112 |
| 9 | 375597 |
| 10 | 1316944 |
| 11 | 4544124 |
| 12 | 15474559 |
| 13 | 52108212 |
| 14 | 173799309 |
| 15 | 574908646 |
| 16 | 1888125243 |
| 17 | 6162032375 |
| 18 | 19998659760 |
| 19 | 64584817367 |
| 20 | 207655073310 |
| 21 | 665017743665 |