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Numbers n such that 12345678901098765432*sum(k=1,n,10^(20k-19)) + 1 is prime.
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%I #2 Mar 30 2012 17:36:44

%S 6,16,337

%N Numbers n such that 12345678901098765432*sum(k=1,n,10^(20k-19)) + 1 is prime.

%C The first two terms are given in the linked source in "Table 42: Ten Types of 'Rare' Prime Numbers" for entry "C. Almost-equipandigital prime of the type: (12345678901098765432)n 1", which designates that 12345678901098765432 is concatenated n times and then 1 is appended. 337, found by PrimeForm using recurrence mode, corresponds to a 6741-digit probable prime. There are no other terms <= 3000.

%H R. Ondrejka, <a href="http://www.utm.edu/research/primes/lists/top_ten/">The Top Ten: a Catalogue of Primal Configurations</a>

%Y Cf. A117390.

%K bref,hard,more,nonn

%O 1,1

%A _Rick L. Shepherd_, May 06 2006