A309739 Primes of the form b*10^(2*k) + b*10^k + 1 for 1 <= b <= 9, k >= 0.
3, 5, 7, 11, 13, 17, 19, 331, 661, 881, 991, 20201, 60601, 90901, 2002001, 5005001, 300030001, 600060001, 50000500001, 2000002000001, 8000008000001, 9000009000001, 3000000003000000001, 200000000020000000001, 80000000000800000000001
Offset: 1
Examples
b | Primes of the form b*10^(2*k) + b*10^k + 1 --+------------------------------------------------------------- 1 | 3. 2 | 5, 20201, 2002001, 2000002000001, 200000000020000000001, ... 3 | 7, 331, 300030001, 3000000003000000001. 4 | 5 | 11, 5005001, 50000500001, ... 6 | 13, 661, 60601, 600060001, ... 7 | 8 | 17, 881, 8000008000001, 80000000000800000000001, ... 9 | 19, 991, 90901, 9000009000001, 9000000000009000000000001, ...