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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.

%I A385637 #8 Jul 14 2025 19:36:54
%S A385637 13,17,19,23,29,31,37,41,43,47,53,59,61,67,71,73,79,83,89,97,
%T A385637 44443333444333443343,
%U A385637 55555553333333555555333333555553333355553333555333553353
%N 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.
%C A385637 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.
%C A385637 a(23) has 182 digits and starts with 13 2's followed by 13 9's.
%C A385637 a(24) has 272 digits and starts with 16 9's followed by 16 7's.
%C A385637 a(25), if it exists, has m > 200 and > 40200 digits.
%H A385637 Gonzalo Martínez, <a href="/A385637/b385637.txt">Table of n, a(n) for n = 1..24</a>
%e A385637 For i = 4, j = 3 and m = 4, by concatenating 44443333, 444333, 4433 and 43 the prime 44443333444333443343 is obtained.
%Y A385637 Cf. A385481, A059170, A034845.
%K A385637 nonn,base
%O A385637 1,1
%A A385637 _Gonzalo Martínez_, Jul 05 2025