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) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 2 |
| 5 | 6 |
| 6 | 22 |
| 7 | 102 |
| 8 | 506 |
| 9 | 2952 |
| 10 | 18502 |
| 11 | 131112 |
| 12 | 991226 |
| 13 | 8271792 |
| 14 | 73176262 |
| 15 | 703077552 |
| 16 | 7121578106 |
| 17 | 77437418112 |
| 18 | 883521487942 |
| 19 | 10726837356672 |
| 20 | 136104948161786 |
| 21 | 1825110309733632 |