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 | 18 |
| 3 | 86 |
| 4 | 422 |
| 5 | 2094 |
| 6 | 10438 |
| 7 | 52126 |
| 8 | 260502 |
| 9 | 1302254 |
| 10 | 6510758 |
| 11 | 32552766 |
| 12 | 162761782 |
| 13 | 813804814 |
| 14 | 4069015878 |
| 15 | 20345063006 |
| 16 | 101725282262 |
| 17 | 508626345774 |
| 18 | 2543131597798 |
| 19 | 12715657726846 |
| 20 | 63578288109942 |
| 21 | 317891439501134 |