skip every 3 numbers in a list

skip3.rb

(1..18).step(3) {|i| puts (i..i+2).to_a.inspect if i.even?}

# Breaking it down: 

# #step(3) yields every 3rd element in the range, so you start with 1, 4, 7, 10...

# in the block, we want to print lists of 3's, so we do (i..i+2).to_a. Giving us: [1,2,3], [4,5,6], [7,8,9]...

# now we want to skip every other list of 3, so we only print if i is even.