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 | 0 |
| 4 | -3 |
| 5 | -9 |
| 6 | -15 |
| 7 | -6 |
| 8 | 57 |
| 9 | 231 |
| 10 | 501 |
| 11 | 474 |
| 12 | -1223 |
| 13 | -7331 |
| 14 | -19655 |
| 15 | -27813 |
| 16 | 19089 |
| 17 | 248541 |
| 18 | 819141 |
| 19 | 1508316 |
| 20 | 417165 |
| 21 | -8314449 |
| 22 | -34737603 |
| 23 | -78646452 |
| 24 | -71651147 |
| 25 | 251348311 |
| 26 | 1461221581 |
| 27 | 3984339966 |
| 28 | 5586567405 |
| 29 | -5424531663 |
| 30 | -59608307151 |
| 31 | -196443394947 |