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%I #12 Sep 13 2024 00:39:06
%S 1,3,27,663,6919
%N Numbers k such that 1.2. ... .k-1.k + 4 is a prime (dot between numbers means concatenation).
%C Each term is odd and next term is greater than 2500. Prime corresponding to the next term has more than 8900 digits. Number of digits of primes corresponding to the four known terms of this sequence are respectively 1,3,45 & 1881.
%C Next term is greater than 25000. - _Michael S. Branicky_, Sep 12 2024
%e 27 is in the sequence because 123456789101112131415161718192021222324252627 + 4 is a prime.
%Y Cf. A099081, A099082, A099083.
%K base,more,nonn
%O 1,2
%A _Farideh Firoozbakht_, Nov 03 2004
%E a(5) from _Michael S. Branicky_, Jun 20 2023