def isprimer(n: int) -> bool:
    """Is n prime?

    >>> isprimer(2)
    True
    >>> tuple( isprimer(x) for x in range(3,11) )
    (True, False, True, False, True, False, False, False)
    """
    def isprime(k: int, coprime: int) -> bool:
        """Is k relatively prime to the value coprime?"""
        if k < coprime*coprime:
            return True
        if k % coprime == 0:
            return False
        return isprime(k, coprime+2)

    if n < 2:
        return False
    if n == 2:
        return True
    if n % 2 == 0:
        return False
    return isprime(n, 3)