A385637 Primes whose decimal expansion consists of the concatenation of m i’s followed by m j’s, ..., iiijjj, iijj and ij, i != j, where 1 <= i, j <= 9 and m > 0.

13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 44443333444333443343, 55555553333333555555333333555553333355553333555333553353

Offset: 1

Author

Gonzalo Martínez, Jul 05 2025

Keywords

• nonn
• base

Comments

Similar to A385481, but the blocks of i's and j's are concatenated from longest length to shortest, where a(n) contains terms of a length not recorded in A385481, such as length 56, 182 and 272.

a(23) has 182 digits and starts with 13 2's followed by 13 9's.

a(24) has 272 digits and starts with 16 9's followed by 16 7's.

a(25), if it exists, has m > 200 and > 40200 digits.

Examples

			For i = 4, j = 3 and m = 4, by concatenating 44443333, 444333, 4433 and 43 the prime 44443333444333443343 is obtained.
		

Links

• Gonzalo Martínez, Table of n, a(n) for n = 1..24

Crossrefs

Cf. A385481, A059170, A034845.