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A217682 Record bases for first finding prime by concatenation of numbers decremented from terms of A217681. 1

%I

%S 2,3,8,9,10,13,14,18,21

%N Record bases for first finding prime by concatenation of numbers decremented from terms of A217681.

%C The partner sequence gives a monotone sequence of numbers that require increasing values of a base of arithmetic before any prime can be found by concatenating numbers decremented in sequence through 1. This sequence gives the record base required by each.

%e When numbers are concatenated in decreasing sequence in binary from each number 2-9 (10 to 1001 in binary), inevitably there is a prime in the sequence: 101 is prime in binary, as is 11101, etc. But this is not the case for 10 (binary 1010). The number represented as 1011002221201211 in base 3, the concatenation of the decimal values 10 down to 4, is a prime (16532797 in decimal). So the record base is 3 for the 2nd entry here.

%Y Cf. A217681.

%K nonn,base,less,more

%O 1,1

%A _James G. Merickel_, Oct 10 2012

%E a(9) added by _James G. Merickel_, May 05 2013

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Last modified September 23 11:51 EDT 2021. Contains 347612 sequences. (Running on oeis4.)