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 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 25 |
| 5 | 151 |
| 6 | 541 |
| 7 | 1471 |
| 8 | 84001 |
| 9 | 925345 |
| 10 | 5682601 |
| 11 | 25177681 |
| 12 | 2245355641 |
| 13 | 35901100951 |
| 14 | 312222474565 |
| 15 | 1917363070351 |
| 16 | 232479594721921 |
| 17 | 4873115730725761 |
| 18 | 54830346428307601 |
| 19 | 430468886732009185 |
| 20 | 65997947903313461401 |
| 21 | 1711564302775814535511 |