pub fn centered_figurate(s: i64, n: i64) -> i64
Return the nth centered figurate number with s sides
Panics if s is less than three
use reikna::figurate::centered_figurate;
let a = centered_figurate(3, 3);
let b = centered_figurate(4, 9);
let c = centered_figurate(8, 5);
assert_eq!(vec![a, b, c], vec![10, 145, 81]);