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 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 4 |
| 5 | 10 |
| 6 | 28 |
| 7 | 96 |
| 8 | 320 |
| 9 | 1436 |
| 10 | 5556 |
| 11 | 28768 |
| 12 | 129600 |
| 13 | 730864 |
| 14 | 3756936 |
| 15 | 23286784 |
| 16 | 132872192 |
| 17 | 910013776 |
| 18 | 5679982288 |
| 19 | 42235062784 |
| 20 | 286769980416 |
| 21 | 2281079563104 |
| 22 | 16732506817280 |
| 23 | 141975748567040 |
| 24 | 1115928688967680 |
| 25 | 10077454948692288 |
| 26 | 84383735744758464 |