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 | 3 |
| 2 | 12 |
| 3 | 54 |
| 4 | 255 |
| 5 | 1239 |
| 6 | 6132 |
| 7 | 30744 |
| 8 | 155628 |
| 9 | 793650 |
| 10 | 4071210 |
| 11 | 20984340 |
| 12 | 108590118 |
| 13 | 563816526 |
| 14 | 2935798680 |
| 15 | 15324533448 |
| 16 | 80164934919 |
| 17 | 420151515255 |
| 18 | 2205762626010 |
| 19 | 11597513662350 |
| 20 | 61060181223195 |
| 21 | 321870918101535 |