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 | 0 |
| 1 | 0 |
| 2 | 1 |
| 3 | 9 |
| 4 | 62 |
| 5 | 390 |
| 6 | 2359 |
| 7 | 14007 |
| 8 | 82412 |
| 9 | 482652 |
| 10 | 2820061 |
| 11 | 16457397 |
| 12 | 95983370 |
| 13 | 559619970 |
| 14 | 3262267891 |
| 15 | 19015581699 |
| 16 | 110836005272 |
| 17 | 646014798840 |
| 18 | 3765295834489 |
| 19 | 21945889348257 |
| 20 | 127910427675542 |
| 21 | 745517838966462 |