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 | 21 |
| 4 | 102 |
| 5 | 579 |
| 6 | 3601 |
| 7 | 24426 |
| 8 | 176858 |
| 9 | 1359906 |
| 10 | 10996740 |
| 11 | 93136545 |
| 12 | 821734072 |
| 13 | 7529402477 |
| 14 | 71404315785 |
| 15 | 699210393923 |
| 16 | 7053151126260 |
| 17 | 73158494370744 |
| 18 | 778922147312076 |
| 19 | 8500606925203992 |
| 20 | 94961268583354364 |
| 21 | 1084632255967292304 |