generate_n is a better iota_n.

iota_n.cc

#include <algorithm>
#include <vector>
#include <iterator>
#include <iostream>

int main()
{
	std::vector<int> v;
	// instead of asking for iota_n(std::back_inserter(v), 10, 1);
	std::generate_n(back_inserter(v), 10, [n = 0]() mutable { return ++n; });

	for (auto i : v)
		std::cout << i << ' ';
	std::cout << std::endl;
}