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 | 5 |
| 1 | 0 |
| 2 | 10 |
| 3 | -10 |
| 4 | 30 |
| 5 | -50 |
| 6 | 110 |
| 7 | -210 |
| 8 | 430 |
| 9 | -850 |
| 10 | 1710 |
| 11 | -3410 |
| 12 | 6830 |
| 13 | -13650 |
| 14 | 27310 |
| 15 | -54610 |
| 16 | 109230 |
| 17 | -218450 |
| 18 | 436910 |
| 19 | -873810 |
| 20 | 1747630 |
| 21 | -3495250 |
| 22 | 6990510 |
| 23 | -13981010 |
| 24 | 27962030 |
| 25 | -55924050 |
| 26 | 111848110 |
| 27 | -223696210 |
| 28 | 447392430 |
| 29 | -894784850 |
| 30 | 1789569710 |
| 31 | -3579139410 |