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 | 0 |
| 4 | 1 |
| 5 | 2 |
| 6 | 20 |
| 7 | 144 |
| 8 | 1265 |
| 9 | 12072 |
| 10 | 126565 |
| 11 | 1445100 |
| 12 | 17875140 |
| 13 | 238282730 |
| 14 | 3407118041 |
| 15 | 52034548064 |
| 16 | 845569542593 |
| 17 | 14570246018686 |
| 18 | 265397214435860 |
| 19 | 5095853023109484 |
| 20 | 102877234050493609 |
| 21 | 2178674876680100744 |
| 22 | 48296053720501168037 |
| 23 | 1118480911876659396600 |