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 | 1 |
| 3 | 2 |
| 4 | 9 |
| 5 | 44 |
| 6 | 385 |
| 7 | 1854 |
| 8 | 18193 |
| 9 | 153656 |
| 10 | 1924641 |
| 11 | 17123930 |
| 12 | 276117721 |
| 13 | 2880135972 |
| 14 | 51150361249 |
| 15 | 738748900694 |
| 16 | 11608748988705 |
| 17 | 198747251005424 |
| 18 | 4029150617813953 |
| 19 | 67937635488741426 |
| 20 | 1607525018948543401 |
| 21 | 32739373317847964060 |
| 22 | 757174325538283357761 |
| 23 | 16444280000832495199982 |