The following numbers were observed: 1.6.11.16.21 How much of it is equal to 2006?

The following numbers were observed: 1.6.11.16.21 How much of it is equal to 2006?

The tolerance is 5
According to the formula, 1 + (n-1) * 5 = 2006
n=402

Among the 2006 natural numbers from 1 to 2006, the number coprime with 26 is 1

Because 26 = 2 × 13, in the 2006 natural numbers from 1 to 2006, all even numbers are not coprime with 26. In odd numbers, all odd numbers are coprime with 26 except the multiple of 13
2006 △ 13 = 154 more than 4, so in the 2006 natural numbers, there are 154 multiples of 13, and the odd and even numbers account for half, so the odd multiples of 13 are 154 △ 2 = 77, and the odd numbers from 1 to 2006 are 2006 △ 2 = 1003, so the coprime numbers with 26 are 1003-77 = 926

Proof: every natural number n greater than 6 can be expressed as the sum of two mutual natural numbers greater than 1

Proof: intuitively, when n ＞ 6, at 2, 3 In n-2, there must be a number a and N coprime (2 ≤ a ≤ n-2), B = n-a ≥ 2, n = a + B, in this case, a and B must be coprime, otherwise a and B have a common divisor d > 1, then D is also a divisor of N, so a and n have a common divisor greater than 1, and a and N are coprime