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 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 1 |
| 5 | 1 |
| 6 | 21 |
| 7 | 71 |
| 8 | 183 |
| 9 | 2101 |
| 10 | 13513 |
| 11 | 64285 |
| 12 | 629949 |
| 13 | 5762615 |
| 14 | 41992107 |
| 15 | 427215283 |
| 16 | 4789958371 |
| 17 | 47283346849 |
| 18 | 540921904725 |
| 19 | 6980052633257 |
| 20 | 85901272312905 |
| 21 | 1129338979629643 |
| 22 | 16398293425501375 |
| 23 | 238339738265039119 |
| 24 | 3588600147767147775 |
| 25 | 58124879519314730741 |