include mpfr.e

function subfactorial(integer n)
    sequence res = repeat(0,n)
    mpz num = mpz_init(1)

    for i=1 to n do
        mpz_mul_si(num,num,i)
        if mpz_odd(num) then
            mpz_sub_ui(num,num,1)
        else
            mpz_add_ui(num,num,1)
        end if
        res[i] = mpz_get_str(num)
--      res[i] = mpz_init_set(num)
    end for
    return res
end function

?extract(subfactorial(20),tagset(9)&20)