Function partition_number 

pub fn partition_number(n: u64) -> u128

Number of integer partitions of n (partition function p(n)).

Uses Euler’s pentagonal number theorem recurrence. Time complexity: O(n^2). For large n (>200), consider memoization.

Examples

use mathverse_core::integer::partition_number;

assert_eq!(partition_number(0), 1);
assert_eq!(partition_number(4), 5);
assert_eq!(partition_number(5), 7);