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 | 21 |
| 3 | 87 |
| 4 | 489 |
| 5 | 2283 |
| 6 | 11901 |
| 7 | 58047 |
| 8 | 294609 |
| 9 | 1459923 |
| 10 | 7338981 |
| 11 | 36576807 |
| 12 | 183238329 |
| 13 | 915128763 |
| 14 | 4578832461 |
| 15 | 22884596367 |
| 16 | 114451679649 |
| 17 | 572172304803 |
| 18 | 2861119804341 |
| 19 | 14304824180727 |
| 20 | 71526445426569 |
| 21 | 357625253564043 |