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 | -1 |
| 2 | -3 |
| 3 | -1 |
| 4 | 45 |
| 5 | 359 |
| 6 | 2037 |
| 7 | 10079 |
| 8 | 46365 |
| 9 | 204119 |
| 10 | 873477 |
| 11 | 3666959 |
| 12 | 15191085 |
| 13 | 62342279 |
| 14 | 254119317 |
| 15 | 1030760639 |
| 16 | 4165958205 |
| 17 | 16792710839 |
| 18 | 67557739557 |
| 19 | 271392171119 |
| 20 | 1089053371725 |
| 21 | 4366669645799 |
| 22 | 17498051254197 |
| 23 | 70086331418399 |
| 24 | 280627721655645 |