using System.Collections.Generic;
public static bool CheckSequence(List<DateTime> source)
=> source.Select((time, i) => (time, i)).All(x => x.time == source[0].AddHours(x.i));
public static void Main()
var sequence1 = new List<DateTime>(){now.AddHours(1), now.AddHours(2), now.AddHours(3)};
var sequence2 = new List<DateTime>(){now.AddHours(1), now.AddHours(3), now.AddHours(3)};
Console.WriteLine(CheckSequence(sequence1));
Console.WriteLine(CheckSequence(sequence2));