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 | 3 |
| 3 | 21 |
| 4 | 221 |
| 5 | 3117 |
| 6 | 54597 |
| 7 | 1136127 |
| 8 | 27293715 |
| 9 | 742143113 |
| 10 | 22512196673 |
| 11 | 753402861159 |
| 12 | 27571631761077 |
| 13 | 1095346704175755 |
| 14 | 46948527167219957 |
| 15 | 2159638211148320085 |
| 16 | 106129271000784614099 |
| 17 | 5549226963359699829711 |
| 18 | 307623817602110038648839 |
| 19 | 18022345501064909362595723 |
| 20 | 1112657716434830018636702797 |