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 | 7 |
| 4 | 36 |
| 5 | 235 |
| 6 | 1792 |
| 7 | 15261 |
| 8 | 141382 |
| 9 | 1401334 |
| 10 | 14694166 |
| 11 | 161714217 |
| 12 | 1857003186 |
| 13 | 22152227989 |
| 14 | 273573165626 |
| 15 | 3488210643709 |
| 16 | 45820081884234 |
| 17 | 618950367384072 |
| 18 | 8585324020132250 |
| 19 | 122127635117014779 |
| 20 | 1779763238159032068 |
| 21 | 26545963246376545934 |