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 | 1 |
| 2 | 1 |
| 3 | 6 |
| 4 | 36 |
| 5 | 240 |
| 6 | 2160 |
| 7 | 20160 |
| 8 | 241920 |
| 9 | 2903040 |
| 10 | 39916800 |
| 11 | 578793600 |
| 12 | 9580032000 |
| 13 | 161902540800 |
| 14 | 3007651046400 |
| 15 | 58845346560000 |
| 16 | 1234444603392000 |
| 17 | 26854400821248000 |
| 18 | 624231436308480000 |
| 19 | 15083992450695168000 |
| 20 | 385614968295997440000 |