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 | 4 |
| 3 | 22 |
| 4 | 148 |
| 5 | 1156 |
| 6 | 10192 |
| 7 | 99688 |
| 8 | 1069168 |
| 9 | 12468208 |
| 10 | 157071424 |
| 11 | 2126386912 |
| 12 | 30797423680 |
| 13 | 475378906432 |
| 14 | 7793485765888 |
| 15 | 135284756985472 |
| 16 | 2479535560687360 |
| 17 | 47860569736036096 |
| 18 | 970606394944476160 |
| 19 | 20635652201785613824 |
| 20 | 459015456156148876288 |
| 21 | 10662527360021306782720 |