-- Spawns 5 Skeletons --
summon Skeleton 199 57 240 
{Riding:{id:FallingSand,
Riding:{id:Skeleton,
Riding:{id:FallingSand,
Riding:{id:Skeleton,
Riding:{id:FallingSand,
Riding:{id:Skeleton,
Riding:{id:FallingSand,
Riding:{id:Skeleton,}}}}}}}}}

-- Spawns 10 Skeletons --
summon Skeleton 199 57 240 
{Riding:{id:FallingSand,
Riding:{id:Skeleton,
Riding:{id:FallingSand,
Riding:{id:Skeleton,
Riding:{id:FallingSand,
Riding:{id:Skeleton,
Riding:{id:FallingSand,
Riding:{id:Skeleton,
Riding:{id:FallingSand,
Riding:{id:Skeleton,
Riding:{id:FallingSand,
Riding:{id:Skeleton,
Riding:{id:FallingSand,
Riding:{id:Skeleton,
Riding:{id:FallingSand,
Riding:{id:Skeleton,
Riding:{id:FallingSand,
Riding:{id:Skeleton,}}}}}}}}}}}}}}}}}}}

-- Spawns 15 Skeletons --
summon Skeleton 199 57 240 
{Riding:{id:FallingSand,
Riding:{id:Skeleton,
Riding:{id:FallingSand,
Riding:{id:Skeleton,
Riding:{id:FallingSand,
Riding:{id:Skeleton,
Riding:{id:FallingSand,
Riding:{id:Skeleton,
Riding:{id:FallingSand,
Riding:{id:Skeleton,
Riding:{id:FallingSand,
Riding:{id:Skeleton,
Riding:{id:FallingSand,
Riding:{id:Skeleton,
Riding:{id:FallingSand,
Riding:{id:Skeleton,
Riding:{id:FallingSand,
Riding:{id:Skeleton,
Riding:{id:FallingSand,
Riding:{id:Skeleton,
Riding:{id:FallingSand,
Riding:{id:Skeleton,
Riding:{id:FallingSand,
Riding:{id:Skeleton,
Riding:{id:FallingSand,
Riding:{id:Skeleton,
Riding:{id:FallingSand,
Riding:{id:Skeleton,}}}}}}}}}}}}}}}}}}}}}}}}}}}}}