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 | 0 |
| 1 | 1 |
| 2 | 3 |
| 3 | 7 |
| 4 | 31 |
| 5 | 173 |
| 6 | 1199 |
| 7 | 9831 |
| 8 | 93303 |
| 9 | 1004817 |
| 10 | 12107795 |
| 11 | 161367055 |
| 12 | 2356740567 |
| 13 | 37428107645 |
| 14 | 642165083775 |
| 15 | 11836940014639 |
| 16 | 233283750994767 |
| 17 | 4895016784086017 |
| 18 | 108952695421053699 |
| 19 | 2563927258693534391 |
| 20 | 63603177623431960239 |
| 21 | 1658851308207579983341 |