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) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 2 |
| 4 | 9 |
| 5 | 40 |
| 6 | 195 |
| 7 | 1056 |
| 8 | 6321 |
| 9 | 41392 |
| 10 | 293607 |
| 11 | 2237920 |
| 12 | 18210093 |
| 13 | 157329096 |
| 14 | 1436630091 |
| 15 | 13810863808 |
| 16 | 139305550065 |
| 17 | 1469959371232 |
| 18 | 16184586405327 |
| 19 | 185504221191744 |
| 20 | 2208841954063317 |
| 21 | 27272621155678840 |
| 22 | 348586218389733555 |
| 23 | 4605223387997411872 |
| 24 | 62797451641106266329 |
| 25 | 882730631284319415504 |