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 | 4 |
| 3 | 18 |
| 4 | 84 |
| 5 | 387 |
| 6 | 1784 |
| 7 | 8228 |
| 8 | 37944 |
| 9 | 174981 |
| 10 | 806940 |
| 11 | 3721270 |
| 12 | 17160940 |
| 13 | 79139079 |
| 14 | 364956336 |
| 15 | 1683025992 |
| 16 | 7761412016 |
| 17 | 35792386313 |
| 18 | 165059516916 |
| 19 | 761185462362 |
| 20 | 3510269016516 |
| 21 | 16187892672139 |
| 22 | 74651791054120 |
| 23 | 344262840164460 |
| 24 | 1587596244438120 |