csharp.csproj

<Project Sdk="Microsoft.NET.Sdk">

    <PropertyGroup>
        <OutputType>Library</OutputType>
        <TargetFramework>net7.0</TargetFramework>
        <ImplicitUsings>enable</ImplicitUsings>
        <Nullable>enable</Nullable>
        <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
        <LangVersion>10</LangVersion>
    </PropertyGroup>
</Project>

fsharp.fsproj

<Project Sdk="Microsoft.NET.Sdk">

    <PropertyGroup>
        <OutputType>Exe</OutputType>
        <TargetFramework>net7.0</TargetFramework>
        <WarnOn>3390;$(WarnOn)</WarnOn>
    </PropertyGroup>

    <ItemGroup>
        <Compile Include="Skynet.fs" />
        <Compile Include="Program.fs" />
    </ItemGroup>

    <ItemGroup>
      <ProjectReference Include="csharp.csproj" />
    </ItemGroup>

    <ItemGroup>
      <PackageReference Include="Hopac" Version="0.5.1" />
    </ItemGroup>
</Project>

Program.cs

namespace csharp
{
    using System.Linq;

    public class Skynet
    {
        static int children = 10;

        static async Task<long> Loop(int level, long num)
        {
            if (level == 0)
            {
                return num;
            }

            var numFirst = num * children;
            var numLast = numFirst + children - 1;
            var lvl1 = level - 1;

            IEnumerable<long> RangeOfNonSmoker(long start, long end)
            {
                var i = start;
                while (i <= end)
                {
                    yield return i++;
                }
            }

            var tasks = RangeOfNonSmoker(numFirst, numLast).Select(x => Loop(lvl1, x));
            var result = await Task.WhenAll(tasks);
            return result.Sum();
        }

        public static long Run(int level)
        {
            return Loop(level, 0).Result;
        }
    }
}

Program.fs

module Bench

open System
open System.Diagnostics

module GC =
    let clean () =
        GC.Collect()
        GC.Collect()

let time name skynet =
    GC.clean ()
    let timer = Stopwatch.StartNew()
    let sum = skynet 9
    printfn $"%s{name} %d{sum} %A{timer.Elapsed}"

do
    for i = 1 to 5 do
        time "Tasks:" csharp.Skynet.Run

    for i = 1 to 5 do
        time "Hopac: " hopac.Skynet.run

Skynet.fs

namespace hopac

module Skynet =

    open Hopac
    open Hopac.Infixes
    open Hopac.Extensions

    let children = 10L

    let rec skynet lvl num =
        if lvl = 0 then
            Job.result num
        else
            let numFirst = num * children
            let numLast = numFirst + children - 1L
            let lvl1 = lvl - 1
            
            seq { numFirst..numLast }
            |> Seq.Con.mapJob (skynet lvl1)
            >>- Seq.sum

    let run level =
        skynet level 0L
        |> run