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 | 1 |
| 2 | 0 |
| 3 | 9 |
| 4 | 68 |
| 5 | 845 |
| 6 | 12474 |
| 7 | 218827 |
| 8 | 4435864 |
| 9 | 102030777 |
| 10 | 2625176150 |
| 11 | 74701061831 |
| 12 | 2329237613988 |
| 13 | 78972674630005 |
| 14 | 2892636060014050 |
| 15 | 113828236497224355 |
| 16 | 4789121681108775344 |
| 17 | 214528601554419809777 |
| 18 | 10193616586275094959534 |
| 19 | 512100888749268955942015 |