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 | 9 |
| 3 | 61 |
| 4 | 489 |
| 5 | 3951 |
| 6 | 32661 |
| 7 | 273127 |
| 8 | 2306025 |
| 9 | 19610233 |
| 10 | 167729959 |
| 11 | 1441383219 |
| 12 | 12434998005 |
| 13 | 107632809909 |
| 14 | 934263293679 |
| 15 | 8129320828911 |
| 16 | 70886845397481 |
| 17 | 619288973447049 |
| 18 | 5419332253680705 |
| 19 | 47494787636620701 |
| 20 | 416800775902696839 |