Quanta Magazine Puzzle Formula Tester

quanta.r

f = function(expr){
  x = c(13,26,2,4,6,3,9,12,8,10,5,15,18,14,7,21,24,16)
  failure = FALSE
  for(i in seq_along(x)){
    result = eval(expr)
    if(length(result) != 1) next
    print(sprintf("%s, %s, %s",i,x[i],result))
    if(result != x[i]){
      failure = TRUE
      break
    }
  }
  message = ifelse(failure,"FAILED","PASSED")
  print(message)
}

# test
f(expression(x[i-1] + x[i-2]))