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 | 5 |
| 4 | 29 |
| 5 | 219 |
| 6 | 1999 |
| 7 | 21237 |
| 8 | 257753 |
| 9 | 3519863 |
| 10 | 53408891 |
| 11 | 891437073 |
| 12 | 16231399381 |
| 13 | 320172135555 |
| 14 | 6801360675719 |
| 15 | 154800119634989 |
| 16 | 3758162030450993 |
| 17 | 96941257338316911 |
| 18 | 2647679298725738611 |
| 19 | 76331396373264213417 |
| 20 | 2316420658039348511981 |