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 | 9 |
| 2 | 63 |
| 3 | 408 |
| 4 | 2565 |
| 5 | 15939 |
| 6 | 98670 |
| 7 | 610740 |
| 8 | 3786588 |
| 9 | 23535820 |
| 10 | 146710476 |
| 11 | 917263152 |
| 12 | 5752004349 |
| 13 | 36174046743 |
| 14 | 228124619100 |
| 15 | 1442387942520 |
| 16 | 9142452842985 |
| 17 | 58083251802345 |
| 18 | 369816259792035 |
| 19 | 2359448984037600 |