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 | 1 |
| 2 | 4 |
| 3 | 24 |
| 4 | 186 |
| 5 | 1745 |
| 6 | 19090 |
| 7 | 237594 |
| 8 | 3305610 |
| 9 | 50736447 |
| 10 | 850285888 |
| 11 | 15430858102 |
| 12 | 301188960996 |
| 13 | 6286897888336 |
| 14 | 139661748755464 |
| 15 | 3288136274970026 |
| 16 | 81747690289414282 |
| 17 | 2139280904017185007 |
| 18 | 58762203796595526676 |
| 19 | 1689933802493155288876 |
| 20 | 50768897450201657287066 |