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 | 1 |
| 2 | 0 |
| 3 | 1 |
| 4 | 3 |
| 5 | 11 |
| 6 | 61 |
| 7 | 507 |
| 8 | 7442 |
| 9 | 197772 |
| 10 | 9808209 |
| 11 | 902884343 |
| 12 | 153723152913 |
| 13 | 48443147912137 |
| 14 | 28363697921914475 |
| 15 | 30996525982586676021 |
| 16 | 63502034385272108655525 |
| 17 | 244852545421597419740767106 |
| 18 | 1783161611489937453151313949442 |
| 19 | 24603891216883233547700609793901996 |