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 | 2 |
| 2 | 9 |
| 3 | 51 |
| 4 | 323 |
| 5 | 2188 |
| 6 | 15511 |
| 7 | 113634 |
| 8 | 853467 |
| 9 | 6536382 |
| 10 | 50852019 |
| 11 | 400763223 |
| 12 | 3192727797 |
| 13 | 25669818476 |
| 14 | 208023278209 |
| 15 | 1697385471211 |
| 16 | 13933569346707 |
| 17 | 114988706524270 |
| 18 | 953467954114363 |
| 19 | 7939655757745265 |
| 20 | 66368199913921497 |