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 | 4 |
| 2 | 22 |
| 3 | 111 |
| 4 | 570 |
| 5 | 2917 |
| 6 | 15112 |
| 7 | 78900 |
| 8 | 416525 |
| 9 | 2221529 |
| 10 | 11974498 |
| 11 | 65211746 |
| 12 | 358742016 |
| 13 | 1992975905 |
| 14 | 11178149883 |
| 15 | 63279615534 |
| 16 | 361464920864 |
| 17 | 2082869242399 |
| 18 | 12104344580384 |
| 19 | 70924864962233 |
| 20 | 418922049779244 |