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 | -3 |
| 2 | 0 |
| 3 | -1 |
| 4 | -3 |
| 5 | -9 |
| 6 | -28 |
| 7 | -90 |
| 8 | -297 |
| 9 | -1001 |
| 10 | -3432 |
| 11 | -11934 |
| 12 | -41990 |
| 13 | -149226 |
| 14 | -534888 |
| 15 | -1931540 |
| 16 | -7020405 |
| 17 | -25662825 |
| 18 | -94287120 |
| 19 | -347993910 |
| 20 | -1289624490 |
| 21 | -4796857230 |
| 22 | -17902146600 |
| 23 | -67016296620 |
| 24 | -251577050010 |
| 25 | -946844533674 |
| 26 | -3572042254128 |
| 27 | -13505406670700 |