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 | 2 |
| 3 | 15 |
| 4 | 76 |
| 5 | 665 |
| 6 | 5286 |
| 7 | 56287 |
| 8 | 597080 |
| 9 | 7601841 |
| 10 | 99702730 |
| 11 | 1484554511 |
| 12 | 23049638052 |
| 13 | 393702612745 |
| 14 | 7036703742446 |
| 15 | 135702811542495 |
| 16 | 2737989749177776 |
| 17 | 58848546456947297 |
| 18 | 1321063959370833810 |
| 19 | 31310238786268648591 |
| 20 | 773291778432688011260 |
| 21 | 20031956775840631151481 |