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 | 0 |
| 3 | 0 |
| 4 | 2 |
| 5 | 10 |
| 6 | 32 |
| 7 | 96 |
| 8 | 448 |
| 9 | 1968 |
| 10 | 7320 |
| 11 | 21516 |
| 12 | 118938 |
| 13 | 662742 |
| 14 | 4556360 |
| 15 | 26950038 |
| 16 | 155388246 |
| 17 | 756995286 |
| 18 | 5730299976 |
| 19 | 38809702892 |
| 20 | 337875402936 |
| 21 | 2593543573702 |
| 22 | 20560179519176 |
| 23 | 138677553274430 |
| 24 | 1337517942958934 |
| 25 | 11083936316867572 |
| 26 | 94288296012340842 |