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 | 2 |
| 2 | 6 |
| 3 | 26 |
| 4 | 142 |
| 5 | 876 |
| 6 | 5790 |
| 7 | 40020 |
| 8 | 285582 |
| 9 | 2087612 |
| 10 | 15551620 |
| 11 | 117629724 |
| 12 | 900964558 |
| 13 | 6973745924 |
| 14 | 54464010540 |
| 15 | 428645647572 |
| 16 | 3396238954446 |
| 17 | 27067890450300 |
| 18 | 216857021933172 |
| 19 | 1745460025192140 |
| 20 | 14107695302434356 |
| 21 | 114455036696796168 |
| 22 | 931738743735004596 |