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 | 2 |
| 3 | 1 |
| 4 | 5 |
| 5 | -2 |
| 6 | 17 |
| 7 | -23 |
| 8 | 74 |
| 9 | -143 |
| 10 | 365 |
| 11 | -794 |
| 12 | 1889 |
| 13 | -4271 |
| 14 | 9938 |
| 15 | -22751 |
| 16 | 52565 |
| 17 | -120818 |
| 18 | 278513 |
| 19 | -640967 |
| 20 | 1476506 |
| 21 | -3399407 |
| 22 | 7828925 |
| 23 | -18027146 |
| 24 | 41513921 |
| 25 | -95595359 |
| 26 | 220137122 |
| 27 | -506923199 |
| 28 | 1167334565 |