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 | 0 |
| 1 | 0 |
| 2 | 1 |
| 3 | 9 |
| 4 | 91 |
| 5 | 1090 |
| 6 | 15298 |
| 7 | 247352 |
| 8 | 4537132 |
| 9 | 93195696 |
| 10 | 2120623984 |
| 11 | 52973194560 |
| 12 | 1441635171040 |
| 13 | 42464913775232 |
| 14 | 1346297567292416 |
| 15 | 45715740985471744 |
| 16 | 1655552663185480448 |
| 17 | 63698261991541393408 |
| 18 | 2595107348458704209920 |
| 19 | 111613055867327344582656 |