**a(1) = 1, then nonzero digits ( 1 to 9) such that every n-th concatenation is prime if n is prime else it is composite. The previous digits are so chosen that a single digit with prime index gives a prime.**

*1, 1, 3, 1, 1, 2, 1, 1, 1, 2, 9, 1, 1, 1, 1, 4, 3, 4, 3, 1, 1, 1, 3, 1, 1, 1, 1, 4, 1, 2, 3, 1, 1, 1*

*1 seqfan posts*

Index of A-numbers in seqfan: by ascending order by month by frequency by keyword

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