In the first decade of numbers (1-10), there are four prime numbers (2,3,5,7). In the second decade (11-20), there are another four (11,13,17,19).
Are there other such decades with four prime numbers?
Yes, there are.
As an example, the first eight set of decades with 4 prime numbers are:
{5,7,11,13}, {11,13,17,19}, {101, 103, 107, 109}, {191, 193, 197, 199}, {821, 823, 827, 829}, {1481, 1483, 1487, 1489}, {1871, 1873, 1877, 1879}, {2081, 2083, 2087, 2089}
Sources:
(i) Wikipedia: "Prime Quadruplets"
(ii) OEIS sequence A007530: "Prime quadruples: numbers k such that k, k+2, k+6, k+8 are prime"
Edited on June 1, 2022, 11:57 pm
Puzzle Solution
