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) |
|---|---|
| 1 | 4 |
| 2 | 23 |
| 3 | 113 |
| 4 | 582 |
| 5 | 2981 |
| 6 | 15266 |
| 7 | 78188 |
| 8 | 400542 |
| 9 | 2051667 |
| 10 | 10509067 |
| 11 | 53831920 |
| 12 | 275740995 |
| 13 | 1412438656 |
| 14 | 7234951864 |
| 15 | 37059718148 |
| 16 | 189831642853 |
| 17 | 972377820507 |
| 18 | 4980827553280 |
| 19 | 25513377870835 |
| 20 | 130687610786192 |
| 21 | 669423377137934 |