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) |
|---|---|
| 2 | 1 |
| 3 | 0 |
| 4 | 9 |
| 5 | 25 |
| 6 | 70 |
| 7 | 406 |
| 8 | 2093 |
| 9 | 10935 |
| 10 | 41961 |
| 11 | 267751 |
| 12 | 1745040 |
| 13 | 9744384 |
| 14 | 60271016 |
| 15 | 369277000 |
| 16 | 2981920373 |
| 17 | 19297914599 |
| 18 | 136978951579 |
| 19 | 1039245386419 |
| 20 | 8924928983999 |
| 21 | 65392069094065 |
| 22 | 539711448752906 |
| 23 | 4489189106832134 |
| 24 | 39604974257078180 |
| 25 | 404561197077466250 |