The escape sequences are interpreted as single special or other characters, hence the strange output. "\\" means '\' for example.
You can use a raw string literal:
#include <iostream>
int main()
{
std::cout << R"(
_____/\\\\\\\\\________/\\\\\\\\\\\__________/\\\\\\\\\__/\\\\\\\\\\\__/\\\\\\\\\\\_
___/\\\\\\\\\\\\\____/\\\/////////\\\_____/\\\////////__\/////\\\///__\/////\\\///__
__/\\\/////////\\\__\//\\\______\///____/\\\/_______________\/\\\_________\/\\\_____
_\/\\\_______\/\\\___\////\\\__________/\\\_________________\/\\\_________\/\\\_____
_\/\\\\\\\\\\\\\\\______\////\\\______\/\\\_________________\/\\\_________\/\\\_____
_\/\\\/////////\\\_________\////\\\___\//\\\________________\/\\\_________\/\\\_____
_\/\\\_______\/\\\__/\\\______\//\\\___\///\\\______________\/\\\_________\/\\\_____
_\/\\\_______\/\\\_\///\\\\\\\\\\\/______\////\\\\\\\\\__/\\\\\\\\\\\__/\\\\\\\\\\\_
_\///________\///____\///////////___________\/////////__\///////////__\///////////__
)" << '\n';
return 0;
}