Bonsoir,
[tex]\begin{array}{c|c|c}Ordre&#boulettes&#allumettes\\1&4=(1+1)&4=2*1*2\\2&(2+1)^2&2*2*3\\3&(3+1)^2&2*3*4\\4&(4+1)^2&2*4*5\\...&..&..\\10&(10+1)^2&2*10*11=220\\...&...&...\\16&(16+1)^2=17^2=289&2*16*17=544\\...&...&...\\n&(n+1)^2&2*n(n+1)\\\end{array}\\[/tex]