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 | 1 |
| 2 | -3 |
| 3 | 15 |
| 4 | -82 |
| 5 | 486 |
| 6 | -3090 |
| 7 | 20497 |
| 8 | -140010 |
| 9 | 979131 |
| 10 | -6976603 |
| 11 | 50461716 |
| 12 | -369533691 |
| 13 | 2734423934 |
| 14 | -20414010219 |
| 15 | 153571115619 |
| 16 | -1163003999342 |
| 17 | 8859172575069 |
| 18 | -67835214598017 |
| 19 | 521824159637718 |
| 20 | -4030828937892966 |
| 21 | 31252886542570119 |
| 22 | -243142210911325273 |
| 23 | 1897466281615297698 |