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 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 0 |
| 6 | 20 |
| 7 | 210 |
| 8 | 1400 |
| 9 | 7560 |
| 10 | 36120 |
| 11 | 159390 |
| 12 | 850300 |
| 13 | 9875580 |
| 14 | 170133964 |
| 15 | 2688015330 |
| 16 | 36706233200 |
| 17 | 444802722000 |
| 18 | 4939264076016 |
| 19 | 52543545234534 |
| 20 | 583037908936500 |
| 21 | 7645631225897700 |
| 22 | 124931080233222340 |
| 23 | 2327407301807577066 |
| 24 | 44282377224446369800 |