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 | 4 |
| 4 | 18 |
| 5 | 80 |
| 6 | 357 |
| 7 | 1596 |
| 8 | 7150 |
| 9 | 32096 |
| 10 | 144362 |
| 11 | 650568 |
| 12 | 2937316 |
| 13 | 13286368 |
| 14 | 60205805 |
| 15 | 273290988 |
| 16 | 1242639446 |
| 17 | 5659468736 |
| 18 | 25816338046 |
| 19 | 117945079736 |
| 20 | 539646216188 |
| 21 | 2472638868960 |
| 22 | 11345220210658 |
| 23 | 52124831171544 |
| 24 | 239792244636876 |
| 25 | 1104495824173376 |