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 | 4 |
| 2 | 22 |
| 3 | 121 |
| 4 | 664 |
| 5 | 3643 |
| 6 | 19987 |
| 7 | 109657 |
| 8 | 601624 |
| 9 | 3300760 |
| 10 | 18109345 |
| 11 | 99355414 |
| 12 | 545105209 |
| 13 | 2990674357 |
| 14 | 16408085929 |
| 15 | 90021597712 |
| 16 | 493896002842 |
| 17 | 2709719309845 |
| 18 | 14866649448256 |
| 19 | 81564634762843 |
| 20 | 447497579542135 |