This important piece, exhibited at Documenta 5 in 1972, comprises much of the poetic complexity of Merz's work. The classic Fibonacci sequence, found frequently throughout his oeuvre, corresponds to a series of photographs depicting the same place becoming more and more populated. The presence of the people is highlighted by chromatic interventions made in accordance with the numbers in the sequence. The unofficial title by which the work is known - 'a real sum is a sum of people' only emphasises the artist's intention to associate what seems like an abstract, ideal and cold progression like the neon light, with the naturalistic, physical aspect linked to the existence of the people. It is this human presence that turns the sum into a ‘real’, and therefore true, arithmetical sum.