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 | 15390 |
| 3 | 575160 |
| 4 | 7712820 |
| 5 | 57281580 |
| 6 | 296150580 |
| 7 | 1184012640 |
| 8 | 3944197800 |
| 9 | 11364334080 |
| 10 | 29395745478 |
| 11 | 69157229760 |
| 12 | 151652810580 |
| 13 | 311116423500 |
| 14 | 607158951120 |
| 15 | 1127694969072 |
| 16 | 2020055770530 |
| 17 | 3478103852940 |
| 18 | 5829999042420 |
| 19 | 9467119804680 |
| 20 | 15046034533560 |