$G$3: =((F3+F4+F5)/3)
$G$6: =((F6+F7+F8)/3)
$G$9: =((F9+F10+F11)/3)
$G$12: =((F12+F13+F14)/3)
$G$15: =((F15+F16+F17)/3)
$G$18: =((F18+F19+F20)/3)
$G$21: =((F21+F22+F23)/3)
$G$24: =((F24+F25+F26)/3)
$G$27: =((F27+F28+F29)/3)
$G$30: =((F30+F31+F32)/3)
$G$33: =((F33+F34+F35)/3)
$G$36: =((F36+F37+F38)/3)
$G$39: =((F39+F40+F41)/3)
$G$42: =((F42+F43+F44)/3)
