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 | 13 |
| 4 | 153 |
| 5 | 2089 |
| 6 | 33461 |
| 7 | 620166 |
| 8 | 13097377 |
| 9 | 310957991 |
| 10 | 8205571449 |
| 11 | 238367471761 |
| 12 | 7561422605881 |
| 13 | 260127000028908 |
| 14 | 9647591076297901 |
| 15 | 383769576967012081 |
| 16 | 16299953773597203585 |
| 17 | 736281113282903567521 |
| 18 | 35246262383544562907057 |
| 19 | 1782495208063575448970418 |