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 | 3 |
| 4 | 12 |
| 5 | 68 |
| 6 | 483 |
| 7 | 3946 |
| 8 | 34485 |
| 9 | 315810 |
| 10 | 2984570 |
| 11 | 28907970 |
| 12 | 285601251 |
| 13 | 2868869733 |
| 14 | 29227904840 |
| 15 | 301430074416 |
| 16 | 3141985563575 |
| 17 | 33059739636198 |
| 18 | 350763452126835 |
| 19 | 3749420616902637 |
| 20 | 40348040718155170 |
| 21 | 436827335493148600 |