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 | 0 |
| 2 | 2 |
| 3 | 6 |
| 4 | 26 |
| 5 | 114 |
| 6 | 526 |
| 7 | 2502 |
| 8 | 12194 |
| 9 | 60570 |
| 10 | 305526 |
| 11 | 1560798 |
| 12 | 8058714 |
| 13 | 41987106 |
| 14 | 220470942 |
| 15 | 1165553718 |
| 16 | 6198683090 |
| 17 | 33140219946 |
| 18 | 178012804678 |
| 19 | 960232902606 |
| 20 | 5199384505226 |
| 21 | 28250295397170 |
| 22 | 153977094874862 |
| 23 | 841656387060006 |