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) |
|---|---|
| 1 | 0 |
| 2 | 2 |
| 3 | 5 |
| 4 | 9 |
| 5 | 49 |
| 6 | 259 |
| 7 | 1736 |
| 8 | 13408 |
| 9 | 117664 |
| 10 | 1153714 |
| 11 | 12492569 |
| 12 | 147987413 |
| 13 | 1903194061 |
| 14 | 26402007855 |
| 15 | 392928613560 |
| 16 | 6244069139240 |
| 17 | 105515436903720 |
| 18 | 1889249822655882 |
| 19 | 35726927316484053 |
| 20 | 711526052649064073 |