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 | 0 |
| 2 | 1 |
| 3 | 6 |
| 4 | 57 |
| 5 | 708 |
| 6 | 10905 |
| 7 | 200538 |
| 8 | 4287633 |
| 9 | 104507496 |
| 10 | 2860291089 |
| 11 | 86853807630 |
| 12 | 2897638853769 |
| 13 | 105357244427244 |
| 14 | 4146601837761513 |
| 15 | 175632278607964962 |
| 16 | 7965651564924845985 |
| 17 | 385161391574120046672 |
| 18 | 19778647046883844762017 |
| 19 | 1074979845580061777989014 |