Prime numbers:
2, 3, 5, 7, 11, 13
Multiply each by 19:
38, 57, 95, 133, 209, 247
Subtract from each the sequence of natural numbers 1-6:
38-1=37, 57-2=55, 95-3=92, 133-4=129, 209-5=204, 247-6=241 giving us the sequence:
37, 55, 92, 129, 204, 241, so the missing number is 204.