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 | 0 |
| 2 | 3 |
| 3 | 14 |
| 4 | 63 |
| 5 | 324 |
| 6 | 1955 |
| 7 | 13698 |
| 8 | 109599 |
| 9 | 986408 |
| 10 | 9864099 |
| 11 | 108505110 |
| 12 | 1302061343 |
| 13 | 16926797484 |
| 14 | 236975164803 |
| 15 | 3554627472074 |
| 16 | 56874039553215 |
| 17 | 966858672404688 |
| 18 | 17403456103284419 |
| 19 | 330665665962403998 |
| 20 | 6613313319248079999 |
| 21 | 138879579704209680020 |
| 22 | 3055350753492612960483 |