ιR creates an array 1...R 1↓ drops the first element of whatever is to the right (1...R) R← just assigns the thing to the right to R, so now R is a variable c

ιR creates an array 1...R 1↓ drops the first element of whatever is to the right (1...R) R← just assigns the thing to the right to R, so now R is a variable containing the integers 2...R R∘.×R creates a 2d matrix of every element in R multiplied by every other element in R R∊ takes whatever's to the left (that matrix) and sees if any value in R is in that matrix. it spits out an array that is like 1 0 0 1 0 1 1 0, where the ones correspond to elements in R that are also in the matrix ~ just reverses that list so now we have an array thats like 0 1 1 0 1 0 0 1 which corresponds to elements in R that can't be created by multiplying any two elements of R together / goes through and only returns values of R that correspond to those 1's the flow is like this: R←5 ιR 1 2 3 4 5 1↓1 2 3 4 5 2 3 4 5 R←2 3 4 5 R∘.×R 4 6 8 10 6 9 12 15 8 12 16 20 10 15 20 25 R∊R∘.×R 0 0 1 0 ~R∊R∘.×R 1 1 0 1 1 1 0 1 / 2 3 4 5 2 3 5