Hope I'm not telling my Granny how to "blow eggs" here, but the formula for "ANY @" from ANY number is as follows!!

multiply by the next number down and divide by 2,

i.e, for any 2 from 6,..... =6x5divided by 2, so.... 6x5 divided by 2 = 15.

BY the way the formula for any 3 from 6 = 6x by the next number down x by the next number down, divided by 3, 6x5x4 divided by 3, so 6x5x4= 120 divided by 3= 20

Hope I'm not boring anyone here????