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 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 9 |
| 5 | 68 |
| 6 | 517 |
| 7 | 4163 |
| 8 | 36180 |
| 9 | 341733 |
| 10 | 3512825 |
| 11 | 39238230 |
| 12 | 474788003 |
| 13 | 6199376363 |
| 14 | 86987391878 |
| 15 | 1306291409455 |
| 16 | 20912309745853 |
| 17 | 355604563226196 |
| 18 | 6401691628921841 |
| 19 | 121639267666626943 |
| 20 | 2432850284018404628 |
| 21 | 51090467301893283249 |
| 22 | 1123996221061869232677 |