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 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 9 |
| 5 | 216 |
| 6 | 7570 |
| 7 | 357435 |
| 8 | 22040361 |
| 9 | 1721632024 |
| 10 | 166261966956 |
| 11 | 19459238879565 |
| 12 | 2714812050902545 |
| 13 | 445202898702992496 |
| 14 | 84798391618743138414 |
| 15 | 18567039007438379656471 |
| 16 | 4631381194792101913679985 |
| 17 | 1305719477625154539392776080 |
| 18 | 413153055417968797025496881656 |