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 | 4 |
| 4 | 31 |
| 5 | 293 |
| 6 | 3326 |
| 7 | 44189 |
| 8 | 673471 |
| 9 | 11588884 |
| 10 | 222304897 |
| 11 | 4704612119 |
| 12 | 108897613826 |
| 13 | 2737023412199 |
| 14 | 74236203425281 |
| 15 | 2161288643251828 |
| 16 | 67228358271588991 |
| 17 | 2225173863019549229 |
| 18 | 78087247031912850686 |
| 19 | 2896042595237791161749 |
| 20 | 113184512236563589997407 |