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 | 0 |
| 2 | 1 |
| 3 | 3 |
| 4 | 12 |
| 5 | 58 |
| 6 | 332 |
| 7 | 2232 |
| 8 | 17225 |
| 9 | 150103 |
| 10 | 1458149 |
| 11 | 15623031 |
| 12 | 183012659 |
| 13 | 2326875239 |
| 14 | 31911431853 |
| 15 | 469553925838 |
| 16 | 7378704548888 |
| 17 | 123329776031414 |
| 18 | 2184698889699346 |
| 19 | 40885079221516335 |
| 20 | 806020133224179176 |