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 | 9 |
| 1 | 120 |
| 2 | 753 |
| 3 | 3612 |
| 4 | 15040 |
| 5 | 57366 |
| 6 | 206115 |
| 7 | 709152 |
| 8 | 2360943 |
| 9 | 7659870 |
| 10 | 24340184 |
| 11 | 76031100 |
| 12 | 234116493 |
| 13 | 712166952 |
| 14 | 2143779645 |
| 15 | 6394719216 |
| 16 | 18923041360 |
| 17 | 55601888562 |
| 18 | 162350117703 |
| 19 | 471371537040 |
| 20 | 1361642740059 |