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 | 2 |
| 3 | 2970 |
| 4 | 1321860 |
| 5 | 187430900 |
| 6 | 10199069190 |
| 7 | 269591166222 |
| 8 | 4221404762120 |
| 9 | 44876701584360 |
| 10 | 355148098691850 |
| 11 | 2230178955481730 |
| 12 | 11630998385335692 |
| 13 | 52097117078470620 |
| 14 | 205557074788375310 |
| 15 | 728566149746575350 |
| 16 | 2355657801908655120 |
| 17 | 7034253747275048912 |
| 18 | 19594719516430397970 |