Azure Function to get a number from a Fibonacci sequence. Sample usage: https://functionName.azurewebsites.net/fibonacci?index=14

function.json

{
  "bindings": [
    {
      "authLevel": "anonymous",
      "name": "req",
      "type": "httpTrigger",
      "direction": "in",
      "methods": [
        "get",
        "post"
      ]
    },
    {
      "name": "$return",
      "type": "http",
      "direction": "out"
    }
  ],
  "disabled": false
}

host.json

{
  "version": "2.0",
  "extensions": {
    "http": {
      "routePrefix": ""
    }
  }
}

run.csx

#r "Newtonsoft.Json"

using System.Net;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Primitives;
using Newtonsoft.Json;

public static async Task<IActionResult> Run(HttpRequest req, ILogger log)
{
    string index = req.Query["index"];
    int n;
    bool res = int.TryParse(index, out n);

    return res == true && n>=0 && n<=40
        ? (ActionResult)new OkObjectResult($"{Fibonacci(n)}")
        : new BadRequestObjectResult("Please provide a number between 0 and 40");
}

public static int Fibonacci(int n)
{
    if (n == 0) return 0;
    else if (n == 1) return 1;
    else
    {
        return Fibonacci(n - 1) + Fibonacci(n - 2);
    }
}