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 | 4 |
| 2 | 22 |
| 3 | 156 |
| 4 | 1209 |
| 5 | 10020 |
| 6 | 86724 |
| 7 | 775044 |
| 8 | 7096652 |
| 9 | 66232980 |
| 10 | 627749066 |
| 11 | 6025752664 |
| 12 | 58459917618 |
| 13 | 572315274540 |
| 14 | 5646713239840 |
| 15 | 56091780016288 |
| 16 | 560513824012020 |
| 17 | 5630664768126388 |
| 18 | 56829055796539462 |
| 19 | 575981263878482204 |
| 20 | 5859952654335118851 |