База данных простых чисел до ста миллиардов на коленке

/// <summary>
/// Test only numbers like Size*k + Offsets[i]
/// </summary>
private struct Wheel {
    public int       Size;
    public int[]     Offsets;
    public int[]     Deltas;
    public DivMod[,] DivMods;
}
private static T EratospheneWheel<T>(T consumer, int bound, Wheel wheel)
    where T : struct, IConsumer {
    int low    = (int) Math.Sqrt(bound);
    int length = bound / wheel.Size + 1;
    var sieves = new BitArray[wheel.Offsets.Length];
    for (int i = 0; i < sieves.Length; i++) {
        sieves[i] = new BitArray(length, true);
    }
    int k = 0, num = wheel.Offsets[1], sieve = 1;
    while (num <= low) {
        if (sieves[sieve][k]) {
            consumer.Consume(num);
            for (int other = 0; other < sieves.Length; other++) {
                var divMod = wheel.DivMods[sieve, other];
                var bits   = sieves[divMod.Idx];
                var start = k * (num + wheel.Offsets[other]) + divMod.Div;
                for (int idx = start; idx < length; idx += num) {
                    bits[idx] = false;
                }
            }
        }
        num += wheel.Deltas[sieve];
        sieve++;
        if (sieve == sieves.Length) {
            ++k;
            sieve = 0;
        }
    }
    while (num <= bound) {
        if (sieves[sieve][k]) {
            consumer.Consume(num);
        }
        num += wheel.Deltas[sieve];
        sieve++;
        if (sieve == sieves.Length) {
            ++k;
            sieve = 0;
        }
    }
    return consumer;
}