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 | 5 |
| 3 | 15 |
| 4 | 195 |
| 5 | 663 |
| 6 | 4641 |
| 7 | 16575 |
| 8 | 480675 |
| 9 | 1762475 |
| 10 | 13042315 |
| 11 | 48612265 |
| 12 | 729183975 |
| 13 | 2748462675 |
| 14 | 20809788825 |
| 15 | 79077197535 |
| 16 | 4823709049635 |
| 17 | 18443593425075 |
| 18 | 141400882925575 |
| 19 | 543277076503525 |
| 20 | 8366466978154285 |
| 21 | 32270658344309385 |