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 | 1 |
| 3 | 9 |
| 4 | 44 |
| 5 | 270 |
| 6 | 1938 |
| 7 | 15764 |
| 8 | 143776 |
| 9 | 1453302 |
| 10 | 16128420 |
| 11 | 194980478 |
| 12 | 2550746400 |
| 13 | 35904118874 |
| 14 | 541097840528 |
| 15 | 8693290587030 |
| 16 | 148324680742912 |
| 17 | 2678504175897990 |
| 18 | 51039398650102776 |
| 19 | 1023458322628129882 |