DouKaku?

#include <stdio.h>
#define __USE_GNU
#include <math.h>

void func(int n)
{
    long double d;
    int n_normal, n_plus, n_minus;

    /* exp(pi * sqrt(n)) を求める */
    d = expl(M_PIl * sqrtl((double)n));

    /* 精度倍する。1を加減算して桁上がりするか */
    n_normal = fmodl(d*10000.0, 10000.0);
    n_plus   = n_normal + 1;
    n_minus  = n_normal - 1;

    if ((n_normal % 10000) == 0
     || (n_plus   % 10000) == 0
     || (n_minus  % 10000) == 0) {
        printf("%d %Lf\n", n, d); 
    }   
}

int main()
{
    int n;
                                                                        
    for (n = 1; n < 200; n++) {                                         
        func(n);
    }

    return 0;
}

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <gmp.h>

mpf_t curr, next, bunsi, bunbo;

void mpf_exp(mpf_t x)
{
    unsigned int k;

    mpf_set_ui(curr, 1.0);
    mpf_set_ui(bunsi, 1.0);
    mpf_set_ui(bunbo, 1.0);

    for (k = 1; ;k++) {
        mpf_mul(bunsi, bunsi, x);
        mpf_mul_ui(bunbo, bunbo, k);
        mpf_div(next, bunsi, bunbo);
        mpf_add(next, next, curr);
        if (mpf_cmp(curr, next) == 0) {
            mpf_set(x, curr);
            return;
        }
        mpf_set(curr, next);
    }
}

int main(int argc, char *argv[])
{
    char buf[128], tmp[8];
    double d;
    int i;
    mpf_t x, pi;

    mpf_set_default_prec(128);

    mpf_init(curr);
    mpf_init(next);
    mpf_init(bunsi);
    mpf_init(bunbo);
    mpf_init(x);
    mpf_init(pi);

    mpf_set_str(pi, "3.1415926535897932384626433832795029", 10);

    for (i = 1; i < 200; i++) {
        mpf_set_ui(x, i);
        mpf_sqrt(x, x);
        mpf_mul(x, x, pi);
        mpf_exp(x);

        gmp_sprintf(buf, "%.*Ff", 6, x);
        d = atof(strncpy(tmp, strchr(buf, '.'), 7));
        if ((d < 0.0001) || ((1 - d) < 0.0001))
            printf("%d %s\n", i, buf);
    }

    mpf_clear(curr);
    mpf_clear(next);
    mpf_clear(bunsi);
    mpf_clear(bunbo);
    mpf_clear(x);
    mpf_clear(pi);

    return 0;
}