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 | 0 |
| 2 | 2 |
| 3 | 6 |
| 4 | 22 |
| 5 | 70 |
| 6 | 230 |
| 7 | 742 |
| 8 | 2406 |
| 9 | 7782 |
| 10 | 25190 |
| 11 | 81510 |
| 12 | 263782 |
| 13 | 853606 |
| 14 | 2762342 |
| 15 | 8939110 |
| 16 | 28927590 |
| 17 | 93611622 |
| 18 | 302933606 |
| 19 | 980313702 |
| 20 | 3172361830 |
| 21 | 10265978470 |
| 22 | 33221404262 |
| 23 | 107506722406 |
| 24 | 347899061862 |
| 25 | 1125825013350 |
| 26 | 3643246274150 |
| 27 | 11789792601702 |