Ruby code - 5 lines

Link:

Ruby, pasted on Jul 12:

4.times{|i|
    col = i+1
    row = i+1
    print "_1#{col} * _#{row}1 + "
}

Output:

1	_11 * _11 + _12 * _21 + _13 * _31 + _14 * _41 +