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 | -3 |
| 4 | 13 |
| 5 | 17 |
| 6 | -241 |
| 7 | 121 |
| 8 | 5081 |
| 9 | -13327 |
| 10 | -106705 |
| 11 | 609589 |
| 12 | 1850661 |
| 13 | -23392159 |
| 14 | -6796193 |
| 15 | 811545073 |
| 16 | -1688514383 |
| 17 | -25224774367 |
| 18 | 123764707231 |
| 19 | 650087614573 |
| 20 | -6385330335427 |
| 21 | -9591188592399 |
| 22 | 279171512779759 |
| 23 | -318526766092183 |
| 24 | -10665705513959287 |
| 25 | 40625771132796817 |