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 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 36 |
| 5 | 380 |
| 6 | 6390 |
| 7 | 157962 |
| 8 | 5396888 |
| 9 | 243179064 |
| 10 | 13938711210 |
| 11 | 987858368750 |
| 12 | 84613071940452 |
| 13 | 8597251494954564 |
| 14 | 1020353444641839854 |
| 15 | 139627532137612581090 |
| 16 | 21788453795572514675760 |
| 17 | 3840596246648027262079472 |
| 18 | 758435490711709577216754642 |