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 | 1 |
| 2 | 6 |
| 3 | 42 |
| 4 | 352 |
| 5 | 3470 |
| 6 | 39468 |
| 7 | 509544 |
| 8 | 7367232 |
| 9 | 117981792 |
| 10 | 2073609120 |
| 11 | 39690563616 |
| 12 | 821945839680 |
| 13 | 18312215714832 |
| 14 | 436766423241120 |
| 15 | 11104557643877760 |
| 16 | 299811706265604096 |
| 17 | 8566939116183215232 |
| 18 | 258298187497129564416 |
| 19 | 8195130059917806607104 |
| 20 | 272936837532680503188480 |