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 | 5 |
| 2 | 15 |
| 3 | 60 |
| 4 | 320 |
| 5 | 2151 |
| 6 | 17985 |
| 7 | 176610 |
| 8 | 1985755 |
| 9 | 25116455 |
| 10 | 351852746 |
| 11 | 5393800690 |
| 12 | 89651625560 |
| 13 | 1603780929525 |
| 14 | 30688985052200 |
| 15 | 624900202917151 |
| 16 | 13480450499067220 |
| 17 | 306905745410816990 |
| 18 | 7349620218635161140 |
| 19 | 184589745041317074895 |
| 20 | 4849519725067777296866 |