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 | 0 |
| 2 | 1 |
| 3 | 5 |
| 4 | 21 |
| 5 | 88 |
| 6 | 389 |
| 7 | 1852 |
| 8 | 9525 |
| 9 | 52632 |
| 10 | 310141 |
| 11 | 1936489 |
| 12 | 12749204 |
| 13 | 88149847 |
| 14 | 637769490 |
| 15 | 4812457992 |
| 16 | 37763509549 |
| 17 | 307453610201 |
| 18 | 2592851608305 |
| 19 | 22626572045811 |
| 20 | 204197274002794 |
| 21 | 1905132039608335 |
| 22 | 18370391387293756 |
| 23 | 183001650861913887 |
| 24 | 1882207129695280320 |