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 | 18 |
| 4 | 219 |
| 5 | 4395 |
| 6 | 129280 |
| 7 | 4970984 |
| 8 | 257765641 |
| 9 | 16781325293 |
| 10 | 1348125117404 |
| 11 | 132465548869248 |
| 12 | 15490711962965785 |
| 13 | 2134540479514352751 |
| 14 | 343307151209151099650 |
| 15 | 63606662918084631874716 |
| 16 | 13470938654397531939066909 |
| 17 | 3238387688528230753569245297 |
| 18 | 876825599524773154743990986391 |