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 | 43 |
| 4 | 217 |
| 5 | 1131 |
| 6 | 6017 |
| 7 | 32467 |
| 8 | 177009 |
| 9 | 972691 |
| 10 | 5378425 |
| 11 | 29889531 |
| 12 | 166795977 |
| 13 | 934039419 |
| 14 | 5246059761 |
| 15 | 29540072355 |
| 16 | 166708076001 |
| 17 | 942651407907 |
| 18 | 5339465635049 |
| 19 | 30291114653131 |
| 20 | 172081678284729 |
| 21 | 978807205953931 |