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 | 1 |
| 3 | 3 |
| 4 | 9 |
| 5 | 30 |
| 6 | 128 |
| 7 | 675 |
| 8 | 4231 |
| 9 | 30969 |
| 10 | 258689 |
| 11 | 2428956 |
| 12 | 25306287 |
| 13 | 289620751 |
| 14 | 3610490805 |
| 15 | 48686912930 |
| 16 | 706003798139 |
| 17 | 10953617995740 |
| 18 | 181035032207760 |
| 19 | 3175094503778521 |
| 20 | 58893601709552538 |
| 21 | 1151825702178908788 |
| 22 | 23688535118132456668 |
| 23 | 511050155316058710033 |