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) |
|---|---|
| 1 | 1 |
| 2 | 3 |
| 3 | 15 |
| 4 | 42 |
| 5 | 330 |
| 6 | 390 |
| 7 | 3990 |
| 8 | 9660 |
| 9 | 36540 |
| 10 | 41580 |
| 11 | 595980 |
| 12 | 651420 |
| 13 | 10630620 |
| 14 | 11711700 |
| 15 | 13153140 |
| 16 | 29189160 |
| 17 | 594233640 |
| 18 | 630990360 |
| 19 | 14083949880 |
| 20 | 15015120120 |
| 21 | 16411875480 |
| 22 | 17575838280 |
| 23 | 463140798120 |
| 24 | 484557713640 |
| 25 | 2690500012200 |