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 | 4 |
| 2 | 40 |
| 3 | 320 |
| 4 | 2368 |
| 5 | 16832 |
| 6 | 116608 |
| 7 | 793088 |
| 8 | 5318656 |
| 9 | 35271680 |
| 10 | 231786496 |
| 11 | 1511653376 |
| 12 | 9795518464 |
| 13 | 63126683648 |
| 14 | 404881506304 |
| 15 | 2586017398784 |
| 16 | 16456474427392 |
| 17 | 104381066510336 |
| 18 | 660139718213632 |
| 19 | 4163958223142912 |
| 20 | 26202468819927040 |
| 21 | 164527129801785344 |