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For n = 8: prime(8) = 19 and the numbers 109, 1009 and 10009 are all prime, while 100009 is not. Thus it is possible to insert strings of zeros of lenghts lengths 1, 2 and 3 between all adjacent digits of 19 such that the resulting number is prime. Since 3 is the largest length of such a string in case of 19, a(8) = 3.
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a(n) is the largest k such that when strings of zeros of lengths t = 1..k are inserted between every pair of adjacent digits of prime(n) , the resulting numbers are all primes.
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a(n) is the largest k such that when inserting strings of zeros of lengths t = 1..k are inserted between all every pair of adjacent digits of prime(n), then each the resulting number is primenumbers are all primes.
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