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 | 0 |
| 1 | 4 |
| 2 | 24 |
| 3 | 124 |
| 4 | 624 |
| 5 | 3124 |
| 6 | 15624 |
| 7 | 78124 |
| 8 | 390624 |
| 9 | 1953124 |
| 10 | 9765624 |
| 11 | 48828124 |
| 12 | 244140624 |
| 13 | 1220703124 |
| 14 | 6103515624 |
| 15 | 30517578124 |
| 16 | 152587890624 |
| 17 | 762939453124 |
| 18 | 3814697265624 |
| 19 | 19073486328124 |
| 20 | 95367431640624 |