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 | 1 |
| 2 | 7 |
| 3 | 21 |
| 4 | 87 |
| 5 | 317 |
| 6 | 1215 |
| 7 | 4565 |
| 8 | 17287 |
| 9 | 65261 |
| 10 | 246671 |
| 11 | 931909 |
| 12 | 3521367 |
| 13 | 13305053 |
| 14 | 50272991 |
| 15 | 189953717 |
| 16 | 717732903 |
| 17 | 2711921613 |
| 18 | 10246881583 |
| 19 | 38717399589 |
| 20 | 146292038647 |