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 | 0 |
| 2 | 2 |
| 3 | -1 |
| 4 | 0 |
| 5 | 20 |
| 6 | -1 |
| 7 | -1 |
| 8 | 8 |
| 9 | 0 |
| 10 | 90 |
| 11 | -1 |
| 12 | -1 |
| 13 | 4212 |
| 14 | -1 |
| 15 | -1 |
| 16 | 0 |
| 17 | 272 |
| 18 | 18 |
| 19 | -1 |
| 20 | 5 |
| 21 | -1 |
| 22 | -1 |
| 23 | -1 |
| 24 | -1 |
| 25 | 0 |
| 26 | 650 |
| 27 | -1 |
| 28 | -1 |
| 29 | 142100 |
| 30 | -1 |
| 31 | -1 |
| 32 | 32 |
| 33 | -1 |
| 34 | -1 |
| 35 | -1 |
| 36 | 0 |
| 37 | 1332 |
| 38 | -1 |
| 39 | -1 |
| 40 | 360 |
| 41 | 41984 |
| 42 | -1 |
| 43 | -1 |
| 44 | -1 |
| 45 | 180 |
| 46 | -1 |
| 47 | -1 |
| 48 | -1 |
| 49 | 0 |
| 50 | 50 |
| 51 | -1 |
| 52 | 117 |
| 53 | 1755572 |
| 54 | -1 |
| 55 | -1 |
| 56 | -1 |
| 57 | -1 |
| 58 | 568458 |
| 59 | -1 |
| 60 | -1 |
| 61 | 53872730964 |