struct EveryNth{T<:Integer}
    n::T
    start::T
    stop::T
end

function Base.iterate(i::EveryNth{T}, state=(i.start, zero(T))) where T
    e, c = state
    c > i.stop && return nothing
    e, (e+i.n, c+i.n)
end

Base.length(iter::EveryNth) = Int((iter.stop - iter.start) / iter.n)
Base.eltype(iter::EveryNth{T}) where T = T

iter = EveryNth(2, 0, 10)

length(iter)
eltype(iter)

for i = iter
    println(i)
end