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 | 990 |
| 3 | 58800 |
| 4 | 1047540 |
| 5 | 9762480 |
| 6 | 60458370 |
| 7 | 282458400 |
| 8 | 1073709000 |
| 9 | 3486725280 |
| 10 | 9999899910 |
| 11 | 25937263440 |
| 12 | 61917115260 |
| 13 | 137858120400 |
| 14 | 289254116970 |
| 15 | 576649631040 |
| 16 | 1099510578960 |
| 17 | 2015992480320 |
| 18 | 3570465336750 |
| 19 | 6131063781360 |
| 20 | 10239996799620 |
| 21 | 16679876893680 |