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 | 2 |
| 2 | 5 |
| 3 | 20 |
| 4 | 101 |
| 5 | 620 |
| 6 | 4420 |
| 7 | 35894 |
| 8 | 326946 |
| 9 | 3301574 |
| 10 | 36613057 |
| 11 | 442369756 |
| 12 | 5784470466 |
| 13 | 81391912093 |
| 14 | 1226260443926 |
| 15 | 19696254286261 |
| 16 | 335987466998509 |
| 17 | 6066332690596289 |
| 18 | 115577941857034741 |
| 19 | 2317310520602816401 |
| 20 | 48773396185794559169 |
| 21 | 1075223007090667361164 |