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 | 0 |
| 2 | 1 |
| 3 | 3 |
| 4 | 9 |
| 5 | 30 |
| 6 | 103 |
| 7 | 357 |
| 8 | 1257 |
| 9 | 4494 |
| 10 | 16246 |
| 11 | 59246 |
| 12 | 217719 |
| 13 | 805389 |
| 14 | 2996113 |
| 15 | 11200113 |
| 16 | 42047593 |
| 17 | 158452138 |
| 18 | 599113966 |
| 19 | 2272065638 |
| 20 | 8639763574 |
| 21 | 32933685102 |
| 22 | 125817012366 |
| 23 | 481631387438 |
| 24 | 1847110931703 |
| 25 | 7095928565405 |
| 26 | 27302745922817 |
| 27 | 105204285608025 |